Isty Bitsy's past is mostly unknown. She revealed her name to be Susan Mary, but it is unknown whether this is true. She became a test-subject of the mysterious "Patient Zero", whom gave her DNA from both Spider-Man and Deadpool. As such, she soon begain to mutate.
Itsy Bitsy was created by Joe Kelly and Ed McGuinnes and first appeared (in human form) in Spider-Man/Deadpool issue 8 (2016). She first appeared as Itsy Bitsy one issue later in Spider-Man/Deadpool issue 9 (2016).
Major Story Arcs
When Itsy Bitsy gained her powers, she was tasked by Patient Zero to kill Spider-Man and Deadpool. At first she worked along, following the two heroes. She even assisted them in taking out and even killing a group of villains whom they where fighting. Spider-Man and Deadpool where horrified and tried to stop. Itsy Bitsy then flead the scene. Something however whent wrong, as she turned against her maker afterwards. Her maker fled but was eventually killed by Itsy Bitsy when he asked Spider-Man and Deadpool for help. She told them that she wanted to become a hero and kill the sinners. Obvious to both Spider-Man and Deadpool, Itsy Bitsy was psycotic and they both tried to take her down. Spider-Man planned on killing her but Deadpool killed her instead to save Spider-Man's soul.