the first half of a rhyming phrase with several alternate second halves, all of which connote an activity or a result that is, respectively, simple to perform or achieve.
Tie your shoes? Why that's easy peasy lemon squeezy!
Beat your meat? Why that's easy peasy Japanesey!
As a red-stater, condemn books and films without having read or seen them? Why that's easy peasy puddin'n'pie!