LO has a serious case of the "Mine"s. He seems obsessed with possession...he'll point out everyone's beverage at the table...mama's, daddy's, mine, etc. When he sees a kid anywhere, he'll grab his Thomas that he carries everywhere close to his face and look them in the eye and say "mine". (It's kind of embarassing) Randomly at home he'll do that to us as well with various toys.
To be fair, despite this he's actually pretty good with sharing. He'll always bring you a train or a toy to play with with him, even more than one. And the only one off limits is Thomas.
Recently, when we're putting him to bed he'll get upset if you use his blankets or a pillow on his bed. At that point I'll say that's fine they're yours, but then mommy has to leave. I'm trying to teach him that a meiser doesn't attract people I guess. Well, last night he woke up at 1:30am screaming, and since he's getting his molars, I figured it was time for more Motrin. Nope, he had become a combination of the seagulls on Nemo and Linda Blair. This lasted for a solid 45 minutes, with DH and I trying to calm him down.
If anyone has a suggestion on how to at the very least curb this behavior, I would love to hear it! PLEASE! It's hard because at home he'll share with us, but there's this mine thing...and seriously...they are his, and to be honest, as an adult I'm not trying to take his toys from him or anything. I've seen him at school and he seems fine too, he'll even hand over the truck or other toy he's playing with to someone else.
Re: "Mine" (a little long, sorry)
There is a good, but long article on the Dr. Sear's website about teaching sharing and a shorter article at WebMD.
It sounds like your son is on a great path to having fantastic morals and manners - I wouldn't worry about his case of the "mines".