Wizards of Waverly Place (2007)

S4E5 Three Maxes and a Little Lady

Eager to enhance his skills, Alex enrolls in Justin's wizard class to gain an edge in the competition. Meanwhile, Max becomes a member of an elite wizard society that pressures him to advance the competition date, prompting him to reschedule it for just a few days away. However, upon realizing the society is exploiting him, Max decides to leave. To revert the competition date to its original schedule, Alex and Justin magically transform into Max. Their plan works, but they inadvertently cast a spell that permanently turns Max into a young girl.