Who cares if what they were doing doesn't "sound like them". If their laughing was unwelcomed, than they are doing little more than bullying you.

I used to have this problem back in high school because I was an overweight socially awkward computer geek who didn't care about making friends or how I looked. This didn't start changing until I started caring about myself by losing weight, building confidence, and learning how to stand up for myself.

So yeah, if people were laughing at me like that, my way of dealing with it would be to walk up to them, look them in the eye, and say "is there a problem"? If they still insist on harassing me, I would threaten to report them to their manager.

Id doesn't matter how somebody is "like". What ifs and could bes are meaningless; what matters is the actual facts. If people want to act stupid towards you, than their behavior is what matters and should not be tolerated, regardless of their reasoning.