Saturday wasn't the first time this season that the Royals have worn special uniforms, obviously.
They've had different looks on Mother's Day, Father's Day, Memorial Day and the Salute to the Negro Leagues game.
But the uniforms for the Mariners' anniversary of the "Turn Ahead The Clock" promotion were certainly unique. It's not often that you see players' uniforms without sleeves.
The Mariners won the game 6-4, but did they look better? You decide.
Here are some videos and photos from the game: