Mysterious background characters are cool. Always drop them into adventures. You don't even need to do anything ever again with the vast majority of them. They add verisimilitude, making your campaign setting seem alive and populated with real people.
But when you need someone to suddenly be important, then that shoeshine boy they met three adventures ago can turn out to be someone highly relevant and interesting.
aurilee writes:
Commentary by memnarch (who has not seen the movie)
And the players will never trust background PCs again. Or at least, never trust that shapeshifters they kill are actually dead without personally disintegrating the body afterward. At least Babu can't split themselves into multiple beings. That really would be a nightmare of an adversary.
In retrospect, perhaps we should have been much more suspicious about the frog being. At the same time, it's not exactly surprising the new identity didn't get investigated more. There were at least four different scenes between landing on D'Qar and this one where the players are getting ready to attack the Peace Moon! I mean, why bother to get bogged down with a single background detail when there's a hyperspace cannon planet attack to prepare for? Especially when Jim's character is gathering up explosives.