Baby Bros are similar to the ones seen in the Yoshi's Island series and the game M&L Partners In Time. They appear in almost every level except for the switch palaces and the very first level. The Baby Bros can be killed very easily, even kicking them will count. Kill all 4 of them to obtain a 1-up.
A Koopa's Revenge
Four babies will appear in every level hidden somewhere, They can hurt Koopa if he touches one of them but instantly die after. You can earn bonus points depending on how many you killed in a level
A Koopa's Revenge 2
Like the first game, Babies have been renamed to Baby Bros. and cannot hurt Koopa. They can be killed in several different ways. Kill them all to get the Baby Crusher badge and a 1-UP!
On Version v2.9, They were replaced with Plumber Dolls that behave the exact same way