Malcolm in the middle

The monster seen rising from the water in the opening credits is the monster from 'Clash of the Titans'.

On the show, Reese is the second oldest brother of Malcolm, but in real life, Justin Berfield (Reese) is less than three months younger than Frankie Muniz (Malcolm).

Cloris Leachman (Grandma Ida) and Kenneth Mars (Otto Mannkusser) both use the same German accents they used in 'Young Frankenstein'.