Detachment

After being saved from that robot you discovered your mutant power was the ability to detach body parts at will and if you are in close contact with someone you can detach their parts as well. This makes for some fun practical jokes by switching out people's body parts while they sleep. After nearly a year of training by the X-men, you decide that you want to fight crime in your own way. Luckily later that week of stopping petty thefts and purse snatchers you find a strange help wanted add on your doorstep looking for a sidekick. At least it is from some attractive superheroine.