A three-year-old boy went with his dad to…

A three-year-old boy went with his dad to see a new litter of kittens.
On returning home, he breathlessly informed his mother, “There were two boy kittens and two girl kittens.”

“How did you know that?” his mother asked.

“Daddy picked them up and looked underneath,” he replied.
“I think it’s printed on the bottom!”