The character is brilliant. They might be the hero. They might be the villain. Hell, they might be the love interest, the woobie, a lucky promoted mook, a total jerk (but with a heart of gold), or just some poor cabbage vendor who laments his way into the hearts of fans. No matter what trope they fall under, whether a single trope or many, they all have one thing in common. You love them but the writer doesn't. It's not their fault. They do the best they can. They worm their way into your heart with a Crowning Moment of Awesome or they lambast people with their sharp tongue but it doesn't matter. They just never seem to get the screentime that you think they deserve. Often happens when a single- or few-episode character is introduced and they could have been extremely interesting and could have potentially spawned an interesting plot or new dynamic if made a permanent fixture but was underdeveloped and then discarded. A subtrope of They Wasted a Perfectly Good Plot.
- Apparently people feel this way about Alice from Twilight. If only the series could be about her romance with Bella.
- Angel. The fifth season big bads, The Circle of Black Thorns, are introduced and killed off in just two episodes.
- Stargate SG-1: Linea, the genocidal maniac who could effortlessly hack computers, cure the blind, and make diseases that destroy planets, that had a complete understanding of how the Stargate worked, and was an old lady, seemed like such a cool villain for SG-1 to face. It was their fault she was loose in the first place which adds drama, she is obviously smarter than them, and how often do you see a quiet old lady as a villain anyway? Instead she came back a year later, younger, mindwiped, and redeemed so Daniel could have a rebound girl and then was completely forgotten about all over again.
Hello, Unknown Troper. You'll need to get known to lend a hand here.