(No spoiler cut, but I don't think I'm really giving away any of the plot. :)
I have thought "An Invincible Mother" gave out a Max vibe ever since I first saw the preview for it. After watching it for the third time, I firmly believe this episode would work so much better in the Ultraman Max universe. The focus was on a guest, supernatural character instead of on the main characters. You could replace GUYS with DASH from Max or with any other defense team (well, perhaps not the Night Raider from Nexus; those people were probably too serious for this light heart stuff) and it wouldn't make much difference. (I still love GUYS more than any other defense team, however.) And there were all those random, cute, silly things which had no explanation other than the writers/producers just wanted to throw them in the episode.