[quote=Xzayler]
Well, getting your pant stolen from your hands is still pretty bad as well...Do Natrelmon gain experience only if they fight themselves? E.g do i need to use my Volcan in combat to level him up?
[/quote]

Yes, if you want him to get experience, you need to use him in combat. 

However, the victor in combat typically walks away with 3-7 levels at minimum.