Adam Westing: Most of the celebrities portray over the top versions of themselves. Burt Reynolds is a complete narcissist who has a mirror he stares at in the shower and winks at. Paul Newman is ready to race against anyone despite being in a wheelchair.
Aluminum Christmas Trees: Ha ha! Ashtrays INSIDE by the elevators IN A HOSPITAL! That's funny! Actually, what's funny is that wasn't a joke - it was standard realistic set dressing for a hospital set in the 1970's.
Cake Toppers: The fantasy-segue into a gown-and-tails dance number atop a wedding cake.
The Cameo: Besides the big movie star cameos, other parts are filled with old comedians like Harry Ritz, Charlie Callas, and legendary Borscht Belt standup Henny Youngman (the "there's a fly in my soup" guy).
Clown Elevator: In the hospital Marty is swept away by about 20 doctors and nurse getting off a small elevator.
Droste Image: When the newspaper vendor is wiped out by a bundle, a headline says "Newspaper Vendor Struck Down By Bundle Of Papers Again", and the picture shows...that same paper, with that same headline.
Letting the Air out of the Band: Over a still photo of New York City, the orchestra plays "San Francisco," only to have the conductor (famous movie maestro Lionel Newman) cue them out, instruments trailing off in the process. With a tap of his baton, the orchestra switches to "We'll Have Manhattan."
Mistaken for Gay: Funn, Eggs, and Bell are subjected to this twice by the same duo of women. That said, they were essentially dry humping each other in public the first time.
Murphy's Bed: Various gags during the motel scene; the trope is also lampshaded by a sign at the motel itself.
Featuring Murphy Beds: Charming to the unsophisticated.
No Celebrities Were Harmed: Averted; not only do the various celebrities in the movie cameo as themselves, but they are portrayed in a caustically self-parodying way; Burt Reynolds in particular is presented has an immense Narcissist, who stops before mirrors to strike poses and has a giant billboard with his name and photo on his house.
A Simple Plan / Zany Scheme: Parodied; the absurd strategies Mel and his friends use to contact the stars and get them to play in the movie always work. When they use a straight approach, it always fails.
Though it appears that Burt Reynolds at least only agrees to do the film so they'll stop bugging him.
Something Else Also Rises: When the Engulf & Devour boardmembers are shown a photograph of Bernadette Peters (again, Yummy), as the woman who would be sent to seduce Funn, the table they're sitting at rises several inches.