The Doctor's taking a shower. No big deal.
He's in there for a way long time, though, without really caring that Craig's outside, but then a mysterious bashing booming sound alerts Craig to the upstairs boarder, and he goes to check and make sure the old guy's okay. Soaking wet, the Doctor realizes that Craig is heading up there, and goes slipping and sliding around on the bathroom floor for awhile, and it's fairly excellent. Then he grabs what he thinks is his sonic, but is actually Craig's toothbrush, and runs out in a towel, hair all a mess. But no prob, because the thing upstairs doesn't want Craig, so really it's just the Doctor running around basically naked, which is totally fine at any time.
The Doctor explains, with zero shame, that he was there to save Craig from trouble. "Well? If I ever am, you can come and save me. With my toothbrush." He could, and he would. Welcome home. Sophie shows up and the Doctor waddles over in his towel and gives her a double-cheek kiss hello, and they go inside. Craig's got some kind of football problem, didn't really follow, but anyway could the Doctor substitute on Craig's team? The Doctor sees no problem with that. I hate to say it but at the very least pants are going to be required here. There's a moment where Craig and Sophie sort of awkwardly discuss her role in his life and this football league, it dies down fairly quickly and the Doctor goes to change into his uniform. That is going to be acceptable.
Soph breaks Craig's heart a bit by acknowledging the Doctor's total hotness, but before that can turn into an ugly bloodbath the Doctor sticks his out again, noting that she let herself into the building, which means she has two sets of keys to Craig's house. Neither Sophie nor Craig find this interesting, and the Doctor hides his smile for a bit later. "You must like it here too," he says sweetly. Getting dressed, the Doctor tells Amy what he's about to do, and she laughs her ass off at him, and then he tries to figure out the difference between soccer and lacrosse. (He calls it "the one with the sticks," but wasn't the last cute Doctor into cricket? So it wouldn't be cricket.)
(I don't know what any of these words mean.)
Craig's nervous about telling the team to call him "the Doctor," but of course none of them question it at all, and then there's a moment of wondering about his skill level -- "Where are you strongest?" Arms? -- before they try him out. He is, of course, a whiz at it, because it's all math + luck + last-ditch awesomeness + looking cute, which is pretty much also what the Doctor equals. Cue cheering for the Doctor by everybody, leaguemates, teammates. Sophie. I mean, eventually they're all just cheering Doctor! Doctor! Doctor! Doctor! Rough.