The babies(also known as Baby Bros.) appeared in the first game, A Koopa's Revenge. The babies are:
- Baby Mario (Red hat)
- Baby Luigi (Green hat)
- Baby Wario (Yellow hat)
- Baby Waluigi (Purple hat)
The babies' sprite in the first Koopa's Revenge,they all looks similar,since it was reused from SMW2 Baby Mario.
However in A Koopa's Revenge II,the babies' sprite are now have their own sprites. Baby Wario with his thick eyebrows,the same with Baby Waluigi.
- According to the first AKR,you could not hurt them by moving the Koopa. However,there are now a new ability that you can kick them like kicking loosen-shell Koopas from SMW(before they can move).