Billy appeared in the episode "The Tale of the Thirteenth Floor". He was portrayed by Aaron Ashmore.
Billy lives on the Twelfth floor of an apartment building, with his adopted sister Karin. Ten years prior to the story, his parents adopted his sister, when she was found either lost or forgotten. He was completely unaware, that his sister was actually an alien belonging to a friendly race of Blank Faced Aliens, who had mistakenly left her behind.
On a regular basis, he and his sister would go to play and hang out on the Thirteenth floor. The building elevator operator Gus was very nervous and reluctant to letting them play all by themselves on the Thirteenth floor. Since years ago, the last tenants on that floor just disappeared one day.
He was usually better at most of the sports than she was. So often she would blame her failures on the genetic genes she inherited from her biological family. He would become annoyed hearing her say this, and wanted her to stop using her adoption as an excuse for not being good at things.
One day he found out that a toy company just moved in and set up on the apartment building's thirteenth floor. The most exciting fact was that his sister got an invitation to visit the toy company. He came along with her hoping to have fun, and get some free stuff.
However, what he wasn't aware was that Karin's biological alien parents had returned and were setting up a rescue mission. He thought it was really a toy factory. So he and his sister tested a game where they had to press the right buttons to repeat the right sounds they hear. He was surprised to see that Karin was better at it than he.
Also the game wasn't made for humans, so it started to make him feel, dizzy and zap life and energy out of him. The more he tried, the weaker he became and he soon passed out.
Karin soon woke him up and they made their escape back to their apartment. Then he saw Olga speaking to his sister on the television. Olga says it was supposed to be Karin's rescue. Since she was mistakenly left behind ten years ago. Then he could see Olga turn into a blank faced alien, as she signed off.
He thought it was all crazy talk. So he turned around to ask his sister what they were talking about.
Then suddenly, he could see that his sister had turned into a blank faced alien! Then he ran off screaming.
- Aaron Ashmore also portrayed Jake.