Baby Broly Is the form was assumed when Baby took over the body of Broly. Baby Broly traveled to Earth to get revenge on Goku, and killed any Earthlings on sight, it seemed like he could not be stopped! He first encountered Vegeta, who much to his surprise was knocked aside like a rubber ball. Baby Broly then set his sights on desroying the Earth after several failed attempts of finding Goku. However, much to his dismay Goku had fused with a weakened Vegeta, and became Gogeta (since Goku was told of Baby Broly by Vegeta). Gogeta had been pounding the meat with Baby Broly, so Baby Broly transformed into his 1st, transformation: Super Baby Broly! Super Baby Broly was incredibly slow, which (like Trunks to Cell) led to his downfall. His last transformation would've looked similar to that of Baby Vegeta's 1st form. His speed would have rised to its full peak, and he would have 10x the strength of his previous transformation.
He was killed by a MASSIVE blow to the head.
In his Super Baby Broly state, his power increases, but his speed DECREASES!
His Super Baby Broly form, resembles that of Baby Vegeta's 2nd form which is pretty weird.
He cannot transform into a Golden Great Ape, like Baby Vegeta!
His voice changes dramatically when he changes from Baby Broly to Super Baby Broly.