We used to do remakes of SNL (Saturday Night Live) skits for our highschool assemblies...
or...
How about a kazoo choir :biggrin2:?
A "paint something recognizable" using your feet in 3 minutes competition?
Water-chugging contest?
Hanging a spoon from your nose?
Puppet show with socks?
If you like to dance, you could have audience write out improvisational suggestions for an interpretive dance. Eg. Rabbits. Then go along with whatever they suggest.
(I love doing Improv. Just always say yes!)
Dance around with raincoats and umbrellas to "Its Raining Men!"
Whistling
Mime
My mom usually picks out a song and sticks us in bad costumes and makes us do interpretive dance while we sing a song at family reunions. It gets attention :biggrin2:
Lift an adult with 1 finger (needs about 5-6 kids) Fingers under feet, elbows, and chin
(The list goes on, and on)