Turtle Named Squirtle

Roses are red, lilacs are purple, I have a turtle, his name is Squirtle.

Explanation

Explain Bear

Okay, so listen up, buttercup. This joke works 'cause it sets you up with a classic rhyme scheme. You think it's gonna be all poetic, but then BAM! It hits you with "Squirtle," which is a Pokemon name. It's funny 'cause it's unexpected and kinda dorky. And let's be real, you probably still watch Pokemon, don't you?