Used to emphasize someone else's point, even though it sounds like you are talking about something you just said.
See also: I know, right?
Bob: These guys are just terrible at basketball!
Arthur: I mean, they look like they've never played before!
Randy: I could really go for some Fuji Chen right now.
Derrick: Oh god. I mean, some Sesame Chicken would really hit the spot right now. Mmm.