Dr. Two-Brains is a Mad Scientist from WordGirl and he is the main antagonist. Originally known as Professor Steven Boxleitner, a kind-hearted but distracted scientist, he was turned into the evil Dr. Two-Brains after a botched experiment left his mind merged with an evil lab mouse known as Squeaky. He now spends his time coming up with ways to appease his second mind's hunger and urges, but will make sure to cause as much trouble as possible while doing so.
Professor Boxleitner was the kind-hearted but distracted, and clumsy scientist friend of WordGirl, who let him study her for his book Superheroes and You: A Practical Guide a book that practically made WordGirl the competent hero that we know and love), and would occasionally offer advice to WordGirl when she was at her wit's end.
In The Amazing, Colossal Adventures of WordGirl, the professor had created a device that would hopefully allow people to read the minds of rodents (practically and theoretically, this could possibly be used in conjunction with various medical and experimental tests on lab mice to better understand how the experiments affect them) but when he was distracted by the wafting odor of his pastrami sandwich, his vicious mouse test subject Squeaky hit the "Holy cow, don't press this button!!!" button, and their minds fused.
Boxleitner still exists mentally, but in a Jekyll and Hyde sort of manner. In The Amazing Colossal Adventures of WordGirl, he would occasionally break free and argue with the personality of Dr. Two-Brains; however, these "intrusions" ceased to occur over the course of the show. Two-Brains has also spoken of the mouse mind as a separately thinking persona.
His Personality As Dr. Two-Brains
Due to the mouse brain having a big degree of control over the doctor, Dr. Two-Brains now has an insatiable hunger for cheese, and all of his crimes center around this. He creates a wide assortment of ray guns that vary from increasing or decreasing gravity to turning buildings or hair-gel to cheese. Most of his inventions have a mouse or cheese theme to their appearance, but do not always have a practical villainous use, such as his personal mouse orchestra. He is afraid of cats, as seen in several episodes, due to his mouse instincts.
Two-Brains can also let Squeaky's mind completely take over his body for a certain amount of time. He actually does this in the episode "Mouse Brain Take-Over". However, this ends up in utter chaos, as it turns out Squeaky was more evil and rampant than he is...