I've seen a chess variant where the king and knight switch roles. They switch positions so that there are 2 kings at the b and g-files while only 1 knight on the e-file for each player. The aim is also to Checkmate the knight so the kings can be captured. They still move like how they move in the original game though.
Dead King

Hello people,
Couldn't there be a variation of chess where the king is able to be captured?
There are already lots of such variants that do in fact incorporate that rule. It is as ubiquitous as the rule of 'guarding' (Queen-castling).
Certain 'race' Chess games, for example, sets the condition of victory to the player who could capture all opponent's piece first.
In my own variant, Chaos's Chess, the the "Mother Nature" player's King can be captured: the King doesn't belong to a 'real' player. He doesn't even have a real army.
Hello people,
Couldn't there be a variation of chess where the king is able to be captured?
I don't know what purpose that would serve. Maybe someone who's more creative than me could incorporate it into a variation.
Thanks,
Andrew123Shi