Bart the bat

Bart is a Bat monster that made his first debut in Rampage: Total Destruction. He is one of 30 playable monsters (40 on the Nintendo Wii version). This is the only Rampage game he has appeared in. Bart's special ability enables him to fly upwards on a double jump. This is useful for scaling very tall buildings.

Rampage: Total Destruction (2006)
Bart was just an ordinary human until he participated in a trial of taste testing the latest product of Scumlabs Scum Soda, a green fizzy drink.

Unfortunately, when he consumed the fizzy drink, he began to suffer a violent reaction, of which caused him to mutate into a giant Bat. He then went on a rampage until he was captivated and imprisoned in a Cryo-Tube hidden in Los Angeles.