Below is a list of characters who have been mentioned or pictured, but never appear in person.
Stingy's father is the wealthiest person in LazyTown. In the original Icelandic plays, Stingy's father is the owner of a very popular video rental store. As revealed in the song "Nenni Níski", Stingy gets his father to replace anything he ruins or breaks. Stingy occasionally mentions him in the TV series, but he has never been physically shown. He is seen in a photograph in Stingy's house, albeit with his face covered.
Sportacus 9 is the superhero who served LazyTown before Sportacus 10. He is briefly mentioned by Mayor Meanswell in "Welcome to LazyTown". According to the origin story on the LazyTown Entertainment site, Sportacus 9 had a moustache like the current Sportacus and behaved similarly. He gave a wooden box containing a Sportacus uniform to a kind young boy named Alex, who became Sportacus 10.
Bobby Bird is a famous basketball star, mentioned in "Ziggy's Talking Teddy".