From Muppet Wiki

Toby is the baby in the film Labyrinth. He is Sarah's little brother who was taken by Jareth. According to the Henson.com Featured Character on Toby, his full name is Toby Williams.

In the making-of documentary Inside the Labyrinth, Brian Froud comments that before his son Toby was born, Brian created a picture of a human baby surrounded by goblins, which was part of the inspiration for the film, and when Toby was born, he looked just like the baby in the picture.

A thirteen-year old Toby is the main character in the graphic novel sequel Return to Labyrinth, pictured on the cover with a crown.