[Stan thought he wanted this, but the second Mabel launches herself at him he has second thoughts - namely of that giant whirring portal behind Ford. It's irrational and it's stupid, but the thought of accidentally knocking her in with that shove makes his stomach bottom out.

So even though his arms are raised to shove Ford, he tries to shake Mabel off of him, the journal still in his hands. The whole thing looks a little dumb since the scene wants him to keep moving, and even Ford seems a little unsure of what's happening and why he's not being pushed right now.]

Cut it out! I need that arm!

[He doesn't; he doesn't want to do this at all but he still whines. Dipper catches his ear though, and Stan turns and looks back at him. Is that what this is all about? Forgiving himself? That's...surprisingly tougher than he would have thought it would be.]

It still took me a whole thirty years while he was who knows where! Sure, I got him back, but I'm the one who put him there in the first place, all because I couldn't just take his stupid Journal! If it wasn't for me--

[And with that one reminder of the Journal and how pissed off he was about the whole thing, Stan's unable to fight it any longer. He pushes Ford - even with Mabel on his arm. The Journal gets shoved at Ford but this time when when it slips out of Stan's fingers he immediately pulls Mabel close so she won't go flying and stumbles back.

Ford isn't so lucky - but they already know he isn't. He rises up, exactly the way he has a hundred times today.]