diff --git a/lib/back.js b/lib/back.js
index acf9d3489..a0e4467d7 100644
--- a/lib/back.js
+++ b/lib/back.js
@@ -61,6 +61,7 @@ function Back(fixtureName, options, nockedFn) {
     )
   }
 
+  // TODO-12.x: Replace with `typeof fixtureName === 'string'`.
   if (!_.isString(fixtureName)) {
     throw new Error('Parameter fixtureName must be a string')
   }
@@ -70,7 +71,7 @@ function Back(fixtureName, options, nockedFn) {
   } else if (arguments.length === 2) {
     // If 2nd parameter is a function then `options` has been omitted
     // otherwise `options` haven't been omitted but `nockedFn` was.
-    if (_.isFunction(options)) {
+    if (options instanceof Function) {
       nockedFn = options
       options = {}
     }
@@ -88,7 +89,7 @@ function Back(fixtureName, options, nockedFn) {
   debug('context:', context)
 
   // If nockedFn is a function then invoke it, otherwise return a promise resolving to nockDone.
-  if (_.isFunction(nockedFn)) {
+  if (nockedFn instanceof Function) {
     nockedFn.call(context, nockDone)
   } else {
     return Promise.resolve({ nockDone, context })
@@ -169,7 +170,7 @@ const record = {
     if (context.isRecording) {
       let outputs = recorder.outputs()
 
-      if (typeof options.afterRecord === 'function') {
+      if (options.afterRecord instanceof Function) {
         outputs = options.afterRecord(outputs)
       }
 
diff --git a/lib/common.js b/lib/common.js
index 3a7c6150c..995a06239 100644
--- a/lib/common.js
+++ b/lib/common.js
@@ -170,6 +170,7 @@ function stringifyRequest(options, body) {
 
 function isContentEncoded(headers) {
   const contentEncoding = headers['content-encoding']
+  // TODO-12.x: Replace with `typeof contentEncoding === 'string'`.
   return _.isString(contentEncoding) && contentEncoding !== ''
 }
 
@@ -314,7 +315,7 @@ const noDuplicatesHeaders = new Set([
  */
 function addHeaderLine(headers, name, value) {
   let values // code below expects `values` to be an array of strings
-  if (typeof value === 'function') {
+  if (value instanceof Function) {
     // Function values are evaluated towards the end of the response, before that we use a placeholder
     // string just to designate that the header exists. Useful when `Content-Type` is set with a function.
     values = [value.name]
@@ -359,6 +360,7 @@ function deleteHeadersField(headers, fieldNameToDelete) {
     throw Error('headers must be an object')
   }
 
+  // TODO-12.x: Replace with `typeof fieldNameToDelete !== 'string'`.
   if (!_.isString(fieldNameToDelete)) {
     throw Error('field name must be a string')
   }
@@ -440,6 +442,7 @@ function formatQueryValue(key, value, stringFormattingFn) {
     case value === undefined:
       value = ''
       break
+    // TODO-12.x: Replace with `typeof value === 'string'`.
     case _.isString(value):
       if (stringFormattingFn) {
         value = stringFormattingFn(value)
@@ -453,7 +456,7 @@ function formatQueryValue(key, value, stringFormattingFn) {
       })
       break
     }
-    case _.isObject(value): {
+    case typeof value === 'object': {
       value = Object.entries(value).reduce(function(acc, [subKey, subVal]) {
         const subPair = formatQueryValue(subKey, subVal, stringFormattingFn)
         acc[subPair[0]] = subPair[1]
@@ -473,7 +476,7 @@ function isStream(obj) {
     obj &&
     typeof obj !== 'string' &&
     !Buffer.isBuffer(obj) &&
-    _.isFunction(obj.setEncoding)
+    obj.setEncoding instanceof Function
   )
 }
 
@@ -497,7 +500,7 @@ function normalizeClientRequestArgs(input, options, cb) {
     input = null
   }
 
-  if (typeof options === 'function') {
+  if (options instanceof Function) {
     cb = options
     options = input || {}
   } else {
diff --git a/lib/intercept.js b/lib/intercept.js
index 75b936110..cc2cd7dfe 100644
--- a/lib/intercept.js
+++ b/lib/intercept.js
@@ -52,9 +52,10 @@ let allowNetConnect
  * nock.enableNetConnect(/(google|amazon)/);
  */
 function enableNetConnect(matcher) {
+  // TODO-12.x: Replace with `typeof matcher === 'string'`.
   if (_.isString(matcher)) {
     allowNetConnect = new RegExp(matcher)
-  } else if (_.isObject(matcher) && _.isFunction(matcher.test)) {
+  } else if (matcher instanceof RegExp) {
     allowNetConnect = matcher
   } else {
     allowNetConnect = /.*/
@@ -170,7 +171,7 @@ function interceptorsFor(options) {
         return [
           {
             options: { allowUnmocked: true },
-            matchAddress() {
+            matchOrigin() {
               return false
             },
           },
@@ -389,13 +390,12 @@ function activate() {
     const interceptors = interceptorsFor(options)
 
     if (isOn() && interceptors) {
-      const matches = !!_.find(interceptors, function(interceptor) {
-        return interceptor.matchAddress(options)
-      })
-
-      const allowUnmocked = !!_.find(interceptors, function(interceptor) {
-        return interceptor.options.allowUnmocked
-      })
+      const matches = interceptors.some(interceptor =>
+        interceptor.matchOrigin(options)
+      )
+      const allowUnmocked = interceptors.some(
+        interceptor => interceptor.options.allowUnmocked
+      )
 
       if (!matches && allowUnmocked) {
         let req
diff --git a/lib/intercepted_request_router.js b/lib/intercepted_request_router.js
index 7b898fc01..27e6cecee 100644
--- a/lib/intercepted_request_router.js
+++ b/lib/intercepted_request_router.js
@@ -113,7 +113,7 @@ class InterceptedRequestRouter {
         }
         this.requestBodyBuffers.push(buffer)
       }
-      if (typeof callback === 'function') {
+      if (callback instanceof Function) {
         callback()
       }
     } else {
@@ -131,17 +131,17 @@ class InterceptedRequestRouter {
     debug('req.end')
     const { req } = this
 
-    if (typeof chunk === 'function') {
+    if (chunk instanceof Function) {
       callback = chunk
       chunk = null
-    } else if (typeof encoding === 'function') {
+    } else if (encoding instanceof Function) {
       callback = encoding
       encoding = null
     }
 
     if (!req.aborted && !this.playbackStarted) {
       req.write(chunk, encoding, () => {
-        if (typeof callback === 'function') {
+        if (callback instanceof Function) {
           callback()
         }
         this.startPlayback()
diff --git a/lib/interceptor.js b/lib/interceptor.js
index 0e173defc..a1a865287 100644
--- a/lib/interceptor.js
+++ b/lib/interceptor.js
@@ -110,7 +110,7 @@ module.exports = class Interceptor {
 
   reply(statusCode, body, rawHeaders) {
     // support the format of only passing in a callback
-    if (_.isFunction(statusCode)) {
+    if (statusCode instanceof Function) {
       if (arguments.length > 1) {
         // It's not very Javascript-y to throw an error for extra args to a function, but because
         // of legacy behavior, this error was added to reduce confusion for those migrating.
@@ -126,7 +126,7 @@ module.exports = class Interceptor {
       }
 
       this.statusCode = statusCode || 200
-      if (_.isFunction(body)) {
+      if (body instanceof Function) {
         this.replyFunction = body
         body = null
       }
@@ -213,7 +213,7 @@ module.exports = class Interceptor {
     }
 
     if (reqHeader !== undefined && header !== undefined) {
-      if (_.isFunction(reqHeader)) {
+      if (reqHeader instanceof Function) {
         return reqHeader(header)
       } else if (common.matchStringOrRegexp(header, reqHeader)) {
         return true
@@ -248,7 +248,7 @@ module.exports = class Interceptor {
 
     const requestMatchesFilter = ({ name, value: predicate }) => {
       const headerValue = req.getHeader(name)
-      if (typeof predicate === 'function') {
+      if (predicate instanceof Function) {
         return predicate(headerValue)
       } else {
         return common.matchStringOrRegexp(headerValue, predicate)
@@ -315,7 +315,7 @@ module.exports = class Interceptor {
       matchKey = common.normalizeOrigin(proto, options.host, options.port)
     }
 
-    if (typeof this.uri === 'function') {
+    if (this.uri instanceof Function) {
       matches =
         common.matchStringOrRegexp(matchKey, this.basePath) &&
         // This is a false positive, as `uri` is not bound to `this`.
@@ -352,9 +352,9 @@ module.exports = class Interceptor {
    * Return true when the interceptor's method, protocol, host, port, and path
    * match the provided options.
    */
-  matchAddress(options) {
-    const isRegex = _.isRegExp(this.path)
-    const isRegexBasePath = _.isRegExp(this.scope.basePath)
+  matchOrigin(options) {
+    const isRegex = this.path instanceof RegExp
+    const isRegexBasePath = this.scope.basePath instanceof RegExp
 
     const method = (options.method || 'GET').toUpperCase()
     let { path } = options
@@ -395,7 +395,7 @@ module.exports = class Interceptor {
     debug('Interceptor queries: %j', this.queries)
     debug('    Request queries: %j', reqQueries)
 
-    if (_.isFunction(this.queries)) {
+    if (this.queries instanceof Function) {
       return this.queries(reqQueries)
     }
 
@@ -456,7 +456,7 @@ module.exports = class Interceptor {
       return this
     }
 
-    if (_.isFunction(queries)) {
+    if (queries instanceof Function) {
       this.queries = queries
       return this
     }
@@ -553,7 +553,7 @@ module.exports = class Interceptor {
     if (_.isNumber(opts)) {
       headDelay = opts
       bodyDelay = 0
-    } else if (_.isObject(opts)) {
+    } else if (typeof opts === 'object') {
       headDelay = opts.head || 0
       bodyDelay = opts.body || 0
     } else {
diff --git a/lib/match_body.js b/lib/match_body.js
index 04a28bcff..84753d008 100644
--- a/lib/match_body.js
+++ b/lib/match_body.js
@@ -26,7 +26,7 @@ module.exports = function matchBody(options, spec, body) {
 
   // try to transform body to json
   let json
-  if (typeof spec === 'object' || typeof spec === 'function') {
+  if (typeof spec === 'object' || spec instanceof Function) {
     try {
       json = JSON.parse(body)
     } catch (err) {
@@ -39,7 +39,7 @@ module.exports = function matchBody(options, spec, body) {
     }
   }
 
-  if (typeof spec === 'function') {
+  if (spec instanceof Function) {
     return spec.call(options, body)
   }
 
@@ -56,12 +56,7 @@ module.exports = function matchBody(options, spec, body) {
   // Because the nature of URL encoding, all the values in the body have been cast to strings.
   // dataEqual does strict checking so we we have to cast the non-regexp values in the spec too.
   if (isUrlencoded) {
-    spec = mapValuesDeep(spec, function(val) {
-      if (_.isRegExp(val)) {
-        return val
-      }
-      return `${val}`
-    })
+    spec = mapValuesDeep(spec, val => (val instanceof RegExp ? val : `${val}`))
   }
 
   return common.dataEqual(spec, body)
@@ -73,14 +68,10 @@ module.exports = function matchBody(options, spec, body) {
  */
 function mapValuesDeep(obj, cb) {
   if (Array.isArray(obj)) {
-    return obj.map(function(v) {
-      return mapValuesDeep(v, cb)
-    })
+    return obj.map(v => mapValuesDeep(v, cb))
   }
   if (_.isPlainObject(obj)) {
-    return _.mapValues(obj, function(v) {
-      return mapValuesDeep(v, cb)
-    })
+    return _.mapValues(obj, v => mapValuesDeep(v, cb))
   }
   return cb(obj)
 }
diff --git a/lib/playback_interceptor.js b/lib/playback_interceptor.js
index c0c67fe5d..b1df24c8f 100644
--- a/lib/playback_interceptor.js
+++ b/lib/playback_interceptor.js
@@ -3,7 +3,6 @@
 const util = require('util')
 const zlib = require('zlib')
 const debug = require('debug')('nock.playback_interceptor')
-const _ = require('lodash')
 const common = require('./common')
 const DelayedBody = require('./delayed_body')
 
@@ -100,7 +99,7 @@ function playbackInterceptor({
       interceptor.markConsumed()
 
       let error
-      if (_.isObject(interceptor.errorMessage)) {
+      if (typeof interceptor.errorMessage === 'object') {
         error = interceptor.errorMessage
       } else {
         error = new Error(interceptor.errorMessage)
@@ -271,7 +270,7 @@ function playbackInterceptor({
 
     // Evaluate functional headers.
     common.forEachHeader(response.rawHeaders, (value, fieldName, i) => {
-      if (typeof value === 'function') {
+      if (value instanceof Function) {
         response.rawHeaders[i + 1] = value(req, response, responseBody)
       }
     })
diff --git a/lib/recorder.js b/lib/recorder.js
index f5cf28e2d..ec961a982 100644
--- a/lib/recorder.js
+++ b/lib/recorder.js
@@ -344,10 +344,10 @@ function record(recOptions) {
     const oldEnd = req.end
     req.end = function(chunk, encoding, callback) {
       debug('req.end')
-      if (typeof chunk === 'function') {
+      if (chunk instanceof Function) {
         callback = chunk
         chunk = null
-      } else if (typeof encoding === 'function') {
+      } else if (encoding instanceof Function) {
         callback = encoding
         encoding = null
       }