If the're still making fun of you for stuff you did when you were younger than just try to laugh it off. If they say something about you doing stupid stuff turn around and be like "hey, yea it was fun as hell and I'd do it agian!" 98% of the time people make fun of other people is to get a rise out of them. If they see that they can't get a rise out of you then most likely they will loose interest. It becomes boring. Screw them.