Little Boy and his Mom

The little boy and his mom are recurring characters who appear in six books.

These books are The Adventures of Captain Underpants, Captain Underpants and the Attack of the Talking Toilets, Captain Underpants and the Perilous Plot of Professor Poopypants, Captain Underpants and the Terrifying Re-Turn of Tippy Tinkletrousers, Captain Underpants and the Revolting Revenge of the Radioactive Robo-Boxers, and Captain Underpants and the Sensational Saga of Sir Stinks-A-Lot.

They are voiced by Len Forgione in the Sound-O-Rama Audiobooks.

Personality
The little boy usually notices things (such as seeing Captain Underpants and other unusual things), but his mom doesn't believe him. In the future, Mom sees something, and the boy says, "And I'm the one seeing a therapist?" In the far future, the boy is grown up and the mom is still seeing things. Ironically, the two manage to become the last humans left on Earth in the alternate timeline created by Tippy Tinkletrousers, and the mother still doesn't notice a thing.

Captain Underpants and the Perilous Plot of Professor Poopypants
The little boy appears briefly putting salt in Professor Pippy Pee-Pee Poopypants's coffee when he isn't looking.

Captain Underpants: The First Epic Movie
The little boy makes a cameo appearance, where he is briefly seen in the crowd of students at Jerome Horwitz Elementary School.

The Epic Tales of Captain Underpants
Both the little boy and his mother make a cameo appearance in "The Frenzied Farts of Flabby Flabulous."