One of the best ways to stimulate your creativity is to recreate something that already exists and make it funny. This is done in art, movies, music and more, and you can do it through your writing!
For instance, take the lyrics to your favorite song and make them fit a theme: recess or Pokemon or cooking dinner. You'll get some really funny results -- you can sing along too!
To do this:
Find the lyrics of the song you want to parody and print them out. Then, study the structure of the song--the rhyme scheme, or how the rhyme works in the song, is important to keep intact. Then, pick the theme you want to use and go crazy writing your lyrics or poem!
Here's an example of a song parody of "Gangam Style" written with new lyrics themed after the video game, Minecraft.
http://youtu.be/0t1QXHT2SmE