January 14, 1984
The referee in Tennis for the NES is one of the Mario Brothers. It's not clear which one, but he looks more like Luigi, due to the white cap. He's still present in every re-release of the game, including the NEC PC-8801 Nintendo no Tennis.
Some argue however that this is not Mario, but rather a referee only looking like Mario, making this a Type 3 link.
Tennis (Game Boy)
May 29, 1989
The referee in Tennis for the Game Boy is once again one of the Mario Brothers. This time he's clearly shown to be Mario in closeups and on the game's box.
Copyrights for both series are held by Nintendo.