From Dragon Ball Encyclopedia, the ''Dragon Ball'' wiki
Puck (FUNimation "Puck") is a student at Satan City Primary School.
Dragon Ball GT
Dragon Ball GT: A Hero's Legacy
Puck appeared in Dragon Ball GT: A Hero's Legacy. He was first shown in the school playing around in class, for which he was condemned by the teacher. Later, he was shown several times bullying Goku Jr., the most memorable being the one in which he stole his Rocket Pen.
His view towards Goku Jr. later changed and he accompanied him to Mount Paozu. On the way, they spent a lot of time discussing one another and Puck eventually returned the Rocket Pen to Goku Jr. They both fought against Mamba, a cannibalistic witch, to save themselves.
When Goku Jr. was hanging from a single rope due to the hanging bridge's collapse, Puck nearly gave up his own life in an attempt to save Goku Jr. In the end, both of them met again, when Puck and Son Pan flew from an helicopter, due to the utter resilience of Goku Jr., who was keen to bring his grandma and friend back to life.