Junior looks like any other scallop; he has a purple shell and a red tongue.
Junior apparently hates Krabby Patties, making him one of the few characters that does not like them. He also dislikes donuts and french fries. Instead, he likes to eat worms and ice cream with worms. He also needs to have his diaper changed very often. Junior makes similar crying sounds to a young baby very frequently throughout the episode.
Since Junior has no family to take care of him and is alone, SpongeBob and Patrick become his adoptive parents. He eventually learns to fly at the end of the episode.