Sometimes users are copied with different names by support ie you might find a person with a site event trophy from 2003 but an account less than a year old. This happens sometimes when there is an 'inappropriate username' that tnt doesn't want on the site anymore but they don't want to lose the user completely. I haven't seen this in a long while but perhaps when this happens all their pet's age is reset as well or maybe the pet originally had an inappropriate name and something similar happened with this pet. Also if I remember correctly there are ways to look up your old dome stats, but I don't believe that is possible for pets only accounts. My guess might be far off, but I hope it is useful none the less.