Malcolm in the Middle S04 E10 If Boys Were Girls

"Family. The weirdest people you'll ever meet."

After being rattled by a battle among the boys, a pregnant Lois ponders the consequences of raising another brawling kid. So she fantasizes that her unruly sons have morphed into well-behaved young daughters. Malcolm becomes Mallory, Reese is transformed into Renee and Dewey turns into Daisy.