Put your fingers to the corners of your eyes and pull as directed whilst singing;
"My mum's Chinese" (pull both fingers up)
"My dad's Japanese" (pull both fingers down)
"Look what happened to me!" (pull one finger up and one finger down).
If this visual gag wasn't hilarious enough, imagine a pubescant girl singing "Chinese, Japanese, Mummy please, what are these?" whilst gesturing to her new, pert bahongas!
Boys can gesture to their dirty knees instead, but that's not as funny as TITS.

A demonstration that anything can be turned into violence, if you just put your mind to it.

1. Bully puts fingers to eyes.
2. "Chinese!" *fingers up*
3. "Japanese!" *fingers down*

So far, so normal. However, in this case, this was a signal for everyone in the room to remain absolutely silent. Anyone making a sound would cue for the bully to scream "PROBLEM!!" and kick the victim in the balls as many times as possible.
When taken further, a whole class can do this to a substitute teacher, minus the ball-kicking. The visual aspect of an entire class spring-loading their eyes like a bear trap, coupled with the audio payoff off screaming "PROBLEM!!!" every time s/he tries to speak, is brilliant.

Say:
1) "Chinese" (put your fingers up)
2) "Japanese" (fingers down)
3) "Dirty knees" (touch your knees)
4) "What are these?" (point to your chest)

No one ever replied "tits" or "boobs". They just laughed. Probably because I was about 8 at the time. I suppose they should have said "fried eggs" or "two raisins on an ironing board". But they didn't say that either.