Obsessions: Aaron-video games, Matthew-computer (just likes to type words and such).
With Aaron, I've been through the Pokemon and Star Wars phases as well. Matthew has not had obsessions until recently, and it's really only a mild obsession. If being outdoors were an obsession, I'd say that would be it.
Just gotta ignore Aaron when he has one. There is no talking him out of it. Matthew needs to be removed from the situation (getting harder as he gets bigger) but calms down pretty easily once removed.