Always sucks to create a PC youre excited to play only to be disappointed.
Ive done twists before, sent my players from Faerun to Ravenloft, or incorporated Spelljammer into an ongoing campaign but it always somewhat made sense within the story line and in the end came full circle with the players returning home.
In my current game, my players where in Undermountain and they all jumped into the prismatic wall. Instead of killing them I sent them to Athas, where eventually they fond and unearthed an ancient crashed Spelljammer and used it to return to Faerun. When they returned they found that 110 years had passed and because they didnt complete the mission they were originally on Waterdeep was very different.
I have no objection to weird jaunts; they can be a lot of fun especially around session #xxx when people's interest is flagging. These were one-way trips early in the campaigns without player input.
The universe was explicitly destroyed and we were the only survivors in one going from the Hero System to Chivalry and Sorcery. The Mississippi delta we thought we were on was really a dome in a vast Starlost style spaceship and we found the way out. At least that one kept us in the game system: Aftermath though our equipment very quickly upgraded from scrounged guns to tri-focus laser rifles. The aliens had invaded world wide a la War of the Worlds Tom Cruise edition and the small private detective a la Simon & Simon needed to figure out what they wanted to do (going from a procedural encapsulated adventure style to full blown sandbox).
Yeah, GM. Don't be that guy.