The iguanas weren't meant to be fed human food, but fairly obviously, kids gave them junk food anyway. I wouldn't want to get my fingers caught in an iguana mouth, though. As a kid my elder sister had a blue-tongued lizard, which measured maybe a foot (35cms) and an accidental (or deliberate) bite from one of those was painful enough. These iguanas presumably have jaws which outclass anything i experienced. And in this case, no food was on offer, so a nip might have been offered anyway.