I don't think I need to explain this one much. The group gets into a fight with an enemy who can turn them into frogs, and something happens (like Noct getting washed downstream etc. or just straight up turned into a frog) and his bros rescue the wrong frog thinking its Noctis. Noct recovers and is wondering wtf happened because he's alone now while the bros panic over Not-Noct-Frog. Hilarity and shenanigans ensue.

+Bro Shenanigans
+Frog Shenanigans
+So many Shenanigans
++++Ignis Mother-henning a random frog plz!

Prompto, Gladio, and Ignis actually try to take good care of the frog, going all out like tucking it into bed, feeding it well, etc and freak out when it won't turn back into Noct. Noct's reaction when he finally manages to find his squad again are up to you! Thanks! Have fun with this!