so in your tshl au, the 18 gang's reaction to the Sudden Body Horror hasn't really been covered yet. Are the guys freaking out? trying to get the 12 turtles back to their own dimension before the changes become permanent (likely in vein, since all that already looks pretty irreversible)? Just sticking to fixing the symptoms for now? or some secret fourth thing? Very fun au btw!
Oh yeah, They are. Originally, they were excited to meet other versions of themselves, but after a few weeks, things went to hell. Now, their goal wasn't to show the 2012! Gang the wonders of their world: the hidden city, the crying titans, and New york itself. It was to get them hone as fast as they could before more damage was done.
Raph is panicking, Donnie is rambling, "I can fix it," Mikey is trying to keep everyone together, and Leo...is staring.
So yes, pretty much what you said. Since they don't have the means to bring them back home at the moment, they can only try to ease the pain they are going through.
Though, factor in the Rise!boys being super soldiers, if the 2012 turtles were to, idk, go feral, that might be a problem.
But they've got a cheese grater and some calamari to deal with too. So it might not be there day
In the end, 2012 ended up looking a little👌 different than before, but hey! Cool markings now! And some other additions.