Both Billy and Hoppy are one in the same *spoilers*

For those that don't remember, Hoppy is the teenaged boy that Billy befriends at Tick's gym and later on in the film, Billy informs Tick that Hoppy might be in trouble because he was wearing the same clothes three days in a row. Near the end of the film, Tick informs Billy that Hoppy died while trying to protect his mother from his violent father.

While watching this film, I noticed mirrored similarities between Billy and Hoppy. Both are at a troubling time in their lives right now and both rely on Tick's gym to help them get through it. Hoppy spends his days at the gym to get away from his abusive father and possibly learn boxing to protect his mother and himself and Billy needs to work at Tick's gym to prove to the courts that he's improving his life and fit to be a father. Billy is also re-training with Tick to be a better boxer and win again. Hoppy is trying to get away from a bad father while Billy is trying to be a better father. Basically, both are fighting for better lives.

To further reinforce this theory, look at their names. Billy's last name is "Hope". Hope = Hop-e. Hop-E = Hoppy