Hi Five Ghost and Celia's Son appeared at the end of the finale.
Hi Five Ghost and Celia's son is taller than his father. He looks like Hi Five Ghost, but he has a blue t-shirt and light brown hair.
After the final battle between Pops and Anti-Pops, which resulted in Pops sacrificin himself to destroy his evil twin and save the Universe, the Park returns to Earth after being in space for 3 years. A time montage is shown, which takes place over a course of 25 years, showing the characters' futures. Hi Five Ghost and Celia became DJs, and are seen performing at a concert in Prague.
At the 25 year park reunion, Hi Five Ghost and Celia, who are married, have a son. He appears to be around his teen years. He is even watching Rigby and Eileen's older daughter holding up a piñata, which looks like Pops, and Rigby and Eileen's younger daughter breaks it open, and candy pours out for some of Muscle Man and Starla's kids and him. They pose with their parents and the other Park members and their families for a photo.
- Like Rigby and Eileen's oldest daughter and Mordecai and Stef's Children, Hi Five Ghost and Celia's son is a mix of both his parents' species, in this case, a ghost and a human with light brown hair and a t-shirt.
- Hi Five Ghost and Celia's son was never given a name.
- Along with Mordecai and Stef's children, he does not appear until the reunion.