TJ is shown to be stubborn and somewhat mean to his sister Becky, as most siblings are. However, he is shown to respect and look up to her. He has been described as a nuisance at times. TJ also a soft side, especially toward Word Girl and the popular TV show "The Pretty Princess and Magic Pony Power Hour".
He also seems to have a love for donuts and ice cream, which he often eats large amounts of if he gets the chance.
This and his noticeable belly are traits presumed to be inherited from his father.
TJ has gained weight twice on the show.The first was in the episode "The Homerun King". When he became a "hero" dubbed the Homerun King after stoping a criminal with his baseball by mistake. Under the circumstances, his father allowed him to eat as many donuts as he wanted.
He also had a stuffed gut in "The Straw That Broke Two-Brains' Back" after eating numerous flavors of ice cream. He retained the added weight throughout the entire episode.