pull someone's leg vs play a joke on

pull someone's leg and play a joke on both are verbs.

Word	Noun	Adjective	Verb	Adverb
pull someone's leg	No	No	Yes	No
play a joke on	No	No	Yes	No

As verbs, pull someone's leg and play a joke on are synonyms defined as:

pull someone's leg and play a joke on: subject to a playful hoax or joke

Other synonyms of pull someone's leg include hoax.

pull someone's leg (verb)	play a joke on (verb)
subject to a playful hoax or joke	subject to a playful hoax or joke
	deceive somebody