Chessclub `Promotie' (`Promotion') in Zoetermeer, the Netherlands has for many years each year between Christmas and New Years Eve an `Oliebollen'-tournament. (Oliebollen are a traditional Dutch treat for the end of the year.) In this tournament, several chess variants are played - some existing ones, but also several new ones, just invented for the occasion.
One of such variants, described in a booklet called `Bloemlezing Humorschaak', written by Henk Breugem of SV Promotie, is this variant, called `The disguised king' (De vermomde koning'). The variant is probably invented by Henk Breugem or another member of Chessclub `Promotie'.
In this variant of orthodox chess, the king-piece plays as a normal piece, and can be taken as usual, may put itself into check, etc.
Instead, each player chooses secretly one of his pawns as `royal piece'. This pawn takes the role of king: a player may not put the royal pawn into check, must move the royal king out of check, etc. When the royal pawn is mated, the game is ended. At the end of the game, one can check the notation.
Instead, one can also play that the royal pawn may, if its owner wishes so, be put into check or left into check. As the opponent does not know (but can only guess) which pawn is royal, such a move would be a gamble: one loses instantly when the opponent would choose to take the pawn, but the game would continue if he does not.
Promoting the royal pawn would mean with high probability a draw or better. One should keep a clear track which of ones pawns is royal when it moves.