Back in 2007-2008 (I think) there were these commercials for New Balance shoes called Monster Feet which had the Sesame Street characters on them, I remember there being two commercials for them, one commercial had the Cookie Monster, Oscar the Grouch and Elmo and the other had Grover, Ernie and Bert and Abby Cadabby.
The first of these commercials is available on YouTube but the Second remains unfound...I think it aired during Nick Jr's run during Dora the Explorer...but could be wrong as it aired once and then never again. I think it had something to do with Ernie and Bert not being Monsters.
Monster Feet - TV Spot
The Only know Monster Feet Commerical available to the public.