Right...so, my book is about fictional characters from pop culture falling into the real world, meeting their creators, and having a conflict, which means that every single one is an expy of somebody else.
Atria Silversword is an expy of Selesia Upitiria from Re:Creators (this book actually started as a stealth pitch for a sequel series to it). However, where Selesia is a magic knight who flies a mech, Atria is much more the consummate professional military officer (who happens to pilot a mech).

Princess Stellaria (aka Stella) is an expy of Meteora from Re:Creators. Where Meteora was a JRPG NPC librarian, Stella is a party member who used to drop area of effect spells on monsters. When the story opens, she's been in the world for about five years, lost her powers, and taken up the study of quantum physics.

Captain Infinite is an expy of Superman. In his story, however, time has been allowed to pass. So, as his powers increased and his friends grew old and died, Cap's life has been slowly hollowed out.

Daiki Yamato is an expy of characters like Naofumi from isekai stories like Rising of the Shield Hero. Let's just say he's not going to take learning that this Japan isn't his Japan very well...

The Destroyer is a cliched devil king from a bad Japanese isekai series. His creator cared so little that he didn't even bother giving the man a name.

Jenny Calhoun is an expy of Buffy the Vampire Slayer, and characters like her. She doesn't take the realization that she's a fictional character very well at all.

Jack Death is a rip-off of John Wick. I'm not kidding about that phrasing - he comes from a B-movie series where the producers watched John Wick, wanted in on that action, and decided that what really mattered were the gunfights. So that's all his world is.
And those are my characters, and who they're based on.