I added the “you’ve had” because the question would suggest any character concept you’ve encountered. (In which cause it’s Gaea, the living planet from John Varley’s Titan series.) So what is the wildest character concept in one of our games?

For characters I’ve created, I’ll say it’s a tie between our take on Athena in our last Battlestar Galactica campaign, in which one of the Lords of Kobol essentially resurrected in a host NPC from their ship and who was a cybernetically-enhanced biologically-engineered “god” created by ancient sentient machines at Earth who had destroyed all life on Earth, then had an “oops!” moment and used old DNA to rebirth the human race on Kobol, setting these new Olympians over them to aid in recreating civilization. Her memories were stored in DNA that she could save to bring herself back if killed.

She’s a tie for Constitution, the first sentient starship serving with Starfleet in our Star Trek game. She became sentient over time and finally sued Starfleet for her rights under the Data v Starfleet decision. Connie tended to view her crew as family (but really more like pets) and would get frustrated from time to time  as her FTL switching in her computer cores (look it up) allowed her to “know: what was going to happen before it did, but due to causality, she could not act on an event or answer a question until reality caught up to her computation. Eventually, during a massive Borg invasion, she “woke” the fleet she was with, seeding her mind into the other vessels so they could beat the Borg. They wound up winning the battle with a highly logical and persuasive argument for allowing biological intelligence to choose if they wanted to join with the Borg, thus not only gaining the strength of their cultures and distinctiveness, but that they would be more adaptive by having a free and willing symbiotic relationship. She was considered by the other sentient starships to be their “mother”.