GROBBLE BUBBLE Dan and Arin accidentally bubble each other, and they can't get out. Another dragon comes to help. DIG GRUMPS Arin and Danny dig so deep they go to the Underground, which connects them to the Undertale AU. Write about that.
Grumble Bobble: Danny and Arin roll around for a while, completely lost for what to do. They spend a good while just kind of barking at each other/the world. Then they realize: they’re pretty much made of spikes and claws. And then they just *pop* and everything is hunky-dory again lol
Dig Grumps/Undertrain: I’m kind of way into this. Danny thinks the Underground is actually the center of the earth and that he’s accomplished everything he’s ever dreamed of already. And he and Arin are just exploring the area, when they run into Ross. And Ross is really nice to them, but uncomfortably so. He’s suspiciously welcoming and he’s got this menacing kind of smile that the kids are immediately getting bad vibes from.
Eventually Barry manages to find them and “goddammit Ross you’re not supposed to go off without supervision.” Then he totally sees through Ross’s ruse and shuts it down completely because “no, no you are not going to murder another thing down here stop, bad Ross.”
So they let the dig grumps stay in the house they’d been squatting in (which used to be Toriel’s but she’s...y’know...not around...) until they can figure out how to get them back to the surface without going through that whole spiel with all the fighting and whatnot again. Even if the whole “story” is solved, there are still all the goddamn random encounters and, look, it’s a lot of work.