They mention the appearance of Lunch and Namu in the Dragon Book, but there are actually lots of recycled character models in this episode:
The tiger Goku fights is the pirate that Kame-sennin, Tenshinhan and Chaozu get the dragonball from during the Piccolo Daimao saga (without the eyepatch).
The truck driver is recycled, but we're not sure from where.
The boy is recycled, but again we don't know from where.
The girl walking in front of Namu is the girl Goku gave money to during his first visit to West City.
The boy's mother is Snow's Mother in DragonBall.
The boy's father is Snow's Father in DragonBall (without the moustache).