"Well I guess we can't be that good friends, then. Come on, if we're living together you can do better than that. I'll give you another: favourite movie? Sports team?"

Not that -- either of those would mean anything to someone who wasn't born in the Milky Way, which he's assuming this guy wasn't, but John doesn't much care. He's already half assumed Ianto is lying, that this is some kind of trick.