I'm a Big Boy Now Diapers

I'm a Big Boy Now Diapers is a brand of diapers for older kids.

History
When Ralph clogged the toilet while trying to clean the mop, he saw the water pouring out of the toilet bowl and figured that the mop was wetting itself and needed to put on a pair of I'm a Big Boy Now Diapers. He went into the next room to get a a pair. However, he quickly forgot what he had gone into the room for and became distracted by a toy boat. Ralph then played with the boat by floating it around the room, as the water from the overflowing toilet filled the house.

Behind the Laughter
The name of the diaper brand is a reference to Pull-Ups Training Pants, whose advertising slogan is "I'm a big kid now!"