Actually the expression is "multiplying like rabbits". Rabbits have a gestation period of about 1 month and there are 6-8 baby rabbits per litter. So in one summer a single female rabbit can produce 50-60 young.
they also ovulate on command, see a spry young buck and "pop"
i had a second rabbit for a day until he started to screw my first rabbit. thought he knocked her up right there. this was before we got her fixed, so down to the vet we went for a bunny abortion :devil:
come to think of it, i guess this phrase does hold some meaning, either that or my rabbit is easy