Before he was fused together with Squeaky, Dr. Two-Brains was an ordinary, though easily distracted, a scientist named Steven Boxleitner. He was an ally to WordGirl. Boxleitner was working on an experiment that would help people to read into the minds of rodents. His test subject was Squeaky, an albino lab mouse. While he was hooked up to the machine, Boxleitner was worried about his pastrami sandwich, and left Squeaky, alone, for a second. While he was away, the fiendish mouse saw a button that was entitled "Holy Cow! Don't Press This Button!," and he pressed it. This action fused his brain and Boxleitner's brain. The end result was a hybrid scientist named Dr. Two-Brains. In the episode "Mouse Brain Take-Over," he allowed Squeaky to take control of his mind so that he could cause more chaos. Dr. Two-Brains then reenters his mind and demands him to leave. The reason was that his henchman didn't like the change.
- Out of all of the supervillains Wordgirl has faced, Squeaky is the most eviler villain than Two-Brains and was proven more tough to handle for WordGirl.
- He was responsible and the reason for Dr. Two-Brain's creation and for him and Dr. Boxleitner being turned into Two-Brains.