As usual, Lizzie and her brother Matt are involved in a big fight. ""Fine! I'll stay out of your life!"" they both scream at each other simultaneously. Then, to their amazement, something totally unbelieveable and mysterious happens--their personalities switch bodies, Matt becoming Lizzie and Lizzie becoming Matt! The siblings are horrified by the change, but they are unable to explain it to their parents, so they have no choice but to go to school like everything was normal. Well, not exactly. Matt (as Lizzie) dresses up like Elton John on his worst day and goes around school tripping over his (her) shoes, making better friends with Ethan Craft by talking about guy stuff like scabs and bruises. Gordo and Miranda are mystified by the changes in the girl they think is their old friend Lizzie, especailly after she pulls a revenge prank on Kate. Meanwhile Lizzie (as Matt) slicks her (his) hair down and dresses like a nerd, hoping to stay quiet and attract as little attention as possible. Bu