"your mom is your dad's mom" is a satirical reference to jokes beginning with "your mom is..."
it came from
boredom while walking around target.
if someone is telling "your mom..." jokes, tell them this one, and you
will win, for sure, i promise. they won't know what to say. guaranteed to
work, everytime.
"your mom is so
fat she......blah blah
blah"
"your mom is your dad's mom"
"
wtf?"
----------
*clicks the thumbs down thing*
"yeah? well...your mom is your dad's mom"