I've been searching for several years for this one St. Jude's commercial featuring Jennifer Aniston that I saw maybe twice before they pulled it, but it's no where to be found on youtube or anywhere else I can think of. It went something like:

Child: I hit my head on the trampoline and started getting headaches so my parents took me to the doctor.
Jennifer Aniston: But it wasn't the trampoline was it? (turns to camera) It was a brain tumor.

And I immediately burst into laughter.