Cell Jr. is basically a smaller, blue, kid-sized version of Cell himself. During his fight with Gohan, Cell spawned seven of these creatures to terrorize the Z Fighters and provoke Gohan into losing his cool. It worked—once Gohan finally snapped, he wiped them out almost instantly.
The Cell Juniors don't say much. In the original Japanese, they're limited to just "Ki!" and "Yah!" but the English dubs gave them more personality, having them taunt the Z Fighters with annoying kid-like trash talk.
They've shown up as playable characters in both the Budokai and Budokai Tenkaichi fighting game series.
There's a minor inconsistency between versions: the manga and most of the anime stick with seven Cell Juniors, but in the English dub episode "The Unstoppable Gohan" (episode 186), Gohan actually destroys eight of them.
Content compiled by AnimeList.moe from publicly available sources.
