I think Ellen would be a pretty great cameo--like, maybe the Fraggles would walk by a TV store and see Ellen's talk show on all the screens.
Or maybe she'd walk by, notice them, and say to the person next to her, "Those are some funny-lookin' kids."
Sounds good and the last part is the funniest thing I ever hear.
I don't know who'd be my last choice for a celebrity.
It'd probably do some good to add at least
one Muppeteer cameo.
I bet it would be just right after all the muppet movies have Muppeteer cameos.