I covered castling into mate in one on one of my early blogs.
This is from that blog.
Players castling into mate in one. I have found 116 examples of this on the 1400 database.
I’ll show 4.
Here is the shortest. 7 moves.
Bobla45 - SammyJ, RHP 2008
Next we see White winning easily but stopping mid-attack to defend a lowly g-pawn.
He drops a piece and castles giving Black a happy choice of mate on g2 or h1.
skullinator - TryorFail, RHP 2009 (16 moves)
What comes around goes around - learning from your losses.
In a safe and tepid position Tukumnieks castles and is mated on the spot.
(we see this lad again in the next game)
Tukumnieks - Blanca, RHP 2008 (11 moves)
Here is the longest game (25 moves) it does appear that Black is going
to do the check mating in this game.
Note White’s ultra cunning 24th. move.
Here he can play 24.QxR+ and Qf3 but no, he is waiting for 0-0-0.
This is our hero Tukumnieks in action again, this time he knows the danger
of castling without thinking.
Tukumnieks - sameeh, RHP 2008