g'ed your mellon
You yell it when someone says something stupid and someone else overhears it and now you're both fighting.
"He said my cat is a donut. I'm gonna kill him!", said by a cat lover.
"She said my brother is a failure. I'm gonna beat her up!", said by a proud brother.
"He said my dog smells like a landfill. I'm gonna throw him out the window!", said by a dog owner.