Distillation of the "your mother" insults, which were memorable in themselves for having an element of creativity [here]. Eventually, however, just saying "your mum" (or yomomma) was enough, the implication being that no more needed to be said. She was just yomomma, and that was enough.

I enjoyed "your mum" insults for a goodly while, and even made a quiz in which all the answers were "your mum" related. For instance, What furry animal communicates with a tiny dance? Your mum. What Is The Fastest Land Mammal? Your mum on a bike. How did Marc Bolan die? Your mum farted into his mouth. How much is a guinea and a florin worth? Two gob jobs off your mum. Et, cet, era.

The "Your Mum" game consists of luring your opponent into asking the question "who?" to which you respond with "YOUR MUM!!" and are then the winner. Hours of fun.

The Naim Ditta extension;
Naim threw a peace of paper the Head of Year. When the class was asked 'who threw that?' Naim covered his mouth and shouted 'Your Mum!'.
It should have ended there, but when the head of year asked who said that, Naim replied 'Your Dad'.
It's pathetic, but the idea his mum was somehow in the class, and got grassed up by her husband who for some reason had joined her, was hilarious. It really was.

On the topic of mother insults, this is possibly the funniest graffito I ever saw written with a black magic marker on the wall of the bus shelter. Here it is, exactly as it was written and punctuated:
Douse your mum smell of fish!
I think she douse!
The writer could have simply stated it as a simple fact, i.e. 'your mum smells of fish'. So why did they instead phrase it as they did?
Perhaps the intent was to give their statement a pantomine-like emphasis by phrasing it as a question and then offering up a retort to any arguments that there might be on the subject, as in: "Your mum smells of fish!" (Response: 'Oh no she doesn't!') "Oh yes she does!"
Or perhaps, it was felt necessary to give the reader the opportunity to contest the statement by phrasing it as a question, then, as if imagining what the reply might be, letting them know prematurly that they intend to stand by their conviction, as in: "Do you think that your mum smells of fish? Because even if you don't, I do.".
Or perhaps there was an ongoing debate that the writer decided to settle right there on the bus shelter wall. "There has been some discussion as to whether or not your mum smells of fish. I have done some investigating - which didn't prove too difficult, as you can smell your mother's fishy stank from some distance. So, in conclusion, yes, your mother does stink of the fish."

Basically involved saying "your mum" and repeating what had just been said.

For instance:
Teacher: "..and that's how Jesus died on the cross."
Pupil: "Your mum died on the cross."

Teacher: "Can anybody tell me what happens when you mix these chemicals together?"
Pupil: "Your mum can tell me what happens when you mix these chemicals together."

Hours of fun for all the family!