Fans are pissed after the Season 12 finale of "Supernatural" and they're not holding back. Many took to Twitter, with some threatening to quit watching the CW show.

[SPOILERS! Do not read if you haven't watched the episode yet!]

The last thing fans wanted to see was favorite Castiel (Misha Collins) being killed off in a battle with Satan. Especially as Collins was celebrating his 100th episode as the trench-coated angel. And he might not be quite as popular, but many will miss Crowley (Mark A. Sheppard), who went out with a heroic self-sacrifice. Also getting offed: recurring character Rowena (Ruth Connell).

Of course, being "dead" on this show is often temporary. Both Sam (Jared Padalecki) and Dean (Jensen Ackles) have been to heaven and hell. And Bobby (Jim Beaver) hung out as a ghost after his death. So that definitely leaves the door open for any or all to return.

Still, fans were flipping out:

Is Castiel really gone for good? Collins's nostalgic tweet looking back on the best moments of his character seems kind of ... final.

Then again, Castiel has come back from being killed by Lucifer before. Collins described the gory Season 5 death as "his favorite" to Cinema Blend.