Robert Accettura's
Fun With Wordage

In my opinion, this is the best parody of Avenue Q’s “The Internet is For Porn”. Using Cookie Monster and Prairie Dawn is awesome (not to mention Prairie Dawn is a one of the more obscure characters).
If you find this stuff amusing, here’s Bert and Ernie tries Gangsta-Rap, Bert and Ernie - Ernie I’m [...]

This is disturbing enough to keep me awake for some time, yet still funny.
Edit: Elmo and Andrea Bocelli and Elmo and Robert DeNiro are just slightly less wierd.