Test Tube is a female glass test tube, being shaped of a thin cylinder, with an opening at the top, surrounded by a wider glass ring. Test Tube is a science fanatic, who devotes her life to science and education. She is the most intelligent person in the game, besides Cabby, but very bad at physical challenges. Her knowledge can come off as obnoxious and can irritate the people around her. Her best friend is Fan, while she's close friends with Lightbulb.