1 Monty: Isn’t insulting the Nazis likey to get us in more danger?!
2 Emily: Maybe, but it sure feels good.
3 Prof. Jones: She has a point there, Junior.
4 Emily: How do I say, “Your mother was a hamster and your father smelt of elderberries”?

I did a Google search for "silly insults", and of course all of the top hits were this one. Who am I to fight inevitability?

I did find a lot of discussion about this particular insult, with many people asking what it means. The answers are about evenly divided into two categories:

1. Hamsters are known for breeding rapidly, and elderberries are used in elderberry wine. So the insult is implying that your mother is sexually promiscuous and your father is a drunk. This is incredibly clever and that is why it's so funny.
2. It means nothing at all; it's just deliberately silly. And that silly meaninglessness is incredibly clever and that is why it's so funny.

Take your pick, I guess.