What does "your mom is a hamster" mean?

Question

What does that phrase mean?

Answer 1

It's a quote from Monty Python and the Holy Grail, a humorous English spoof on King Arthur.  

"Your mother is a hampster and your father smelt of elderberries" is one of the insults used in the movie.  

Other famous quotes from that movie:  

"What is the air speed velocity of an unladened swallow?"

"We are the Knights who say...  Ni!"

"It's just a flesh wound."  

"What do we burn apart from witches?  More witches!"

"No, no the peril is much too perilous."

Answer 2

an insult perhaps?

Answer 3

a comedic and easily swallowable insult from Monty Python, which basically says yo' momma' wuz so uglee....

honestly it means nothing except to insult the insultee because the insulter was insulting the insulted.

Sorry I couldn't resist a John Cleese quote.