Hannah the Autistic Detective
One of the strengths of Catch Me, I'm Falling is that each character has an identifiable issue. While the murder and the mystery are central to the game, every character is also on a journey of personal growth. Not all of them will reach the end of that journey (some may even go badly astray) but every one of them has that.
In the aftermath of the con, I learnt that some of the players had taken to referring to one character as "Hannah the Autistic Detective". A player with relevant direct knowledge had looked at the "promotional posters" we (read "my co-writer", who did the great majority of the work here) had created for the characters and identified Hannah as being high-functioning autistic (or Asperger's Syndrome, which some call the same thing, and some don't, and either or both could apply). Yep, that essentially goes to the heart of Hannah's issue. She doesn't necessarily have to be high-functioning autistic - the player gets a say in how dysfunctional Hannah is - but she definitely has problems along those lines.
And Hannah has a journey that stems from that. She is distant, disconnected but very intelligent, and perhaps she can use her unusual talents - particularly the focus people like Hannah often display - to help her friends and to make connections for herself.
All those promotional posters put the characters' issues front-and-centre for the players. I believe the player who first used the phrase "Hannah the Autistic Detective" identified that issue just from the poster; she didn't play the character and hadn't read the character sheet. In other cases... When I was asked by a player if she had to be able to juggle to play the juggler, I pointed out that the juggling in question had nothing to do with the juggling pins. You'd better believe that the character who says "But without you I am nothing," is hurting. Even the strongest character in the troupe is learning how best to apply his strength in new ways.
Not too far out from the con, a moment of revelation for us came when I looked at the posters for certain characters and then called Em and said "We have a problem." What the posters illustrated for me was that we didn't clearly know who certain characters were. Part of that was that we didn't know what their issues were. We talked it over then redesigned the posters and the character sheets to reflect their new issues. Big chunks of both the original posters and the original sheets remain in the game, but they have been rearranged. The result was strong, interesting characters facing real issues.
So, when writing your next game, identify the issue that faces each character. Figure out the proposed journey, or one possible version of it. If you can't do that, what you have is a filler character, and nobody wants to play filler, so find an issue and rewrite. Make it such that players talk about your equivalent of Hannah the Autistic Detective, and not just the one character but preferably several. This is the stuff that makes the game matter to the players.