I mean, a classic example would be the wizard in The Wizard of Oz. No one could say his reality matches the build-up. And, yes, one can say that even though he was ultimately very different, he served an intricate/essential part of the story
I think a character can perform some significant and pivotal act, but still be disappointing in that his/her personality isn't developed, or developed in a satisfying way. Plot isn't everything.
I didn't know he was going to turn out to be a minor character
And when men of mystery appear on TV shows, or in books, etc., eventually the mysteries are solved by the end, usually anyway. That's why we stay tuned.
CN's personal backstory
he disappears in a puff of smoke (not literally... I forget his end) and that's it.
If he'd just been some guy, it wouldn't have mattered, but they drew us in with the frequent mantions of the name with that air of importance, and he had this "presence" and delivery...
suki forbes and julianka were indeed minor characters but for me they created something memorable and unique during their brief stays on the show.claude and demeon not so much...true were both pivotal to the plot of the parallel-time storyline but for they they didn't create a lasting impression given the big buildup they both got(again all i can recall about demeon is that leisure suit).