I realized a bit later that, HEY, crap, I already pulled a very similar moment in the final It’s Walky! battle where somebody jumps in front of a bullet meant for Walky, that time with Grace and Mandy.  Dangit!

Anyway, watch Mike quietly clock that Amber is fighting their own time-travelling child, Donna.   I mean, at this point in the timeline, she hadn’t been conceived yet, so Mike’s mostly noticing, hey, this kid looks like she’s ours.  This is one of those previously-mentioned moments that I wouldn’t have been able to pull off if I’d finished Joyce and Walky! in a timely manner.