Maybe!  Sort of.  It's open to interpretation.
The story goes:  Joe Hawley, a member of SAG, has done a few commercials in his day.  One of them was him singing in a Children's Hospital commercial.  There is an episode of The Simpsons entitled "Rosebud" that briefly mimics the scene Joe did.  Although there's no proof that it was indeed a mock of the commercial, the similarities were enough to get some people, including Joe, wondering about the possibility.
In a July '08 conversation, however, Joe indicated his opinion these days is that the chances are very slim and he doesn't necessarily hold the belief that it's true.