The Mortal Kombat series has been full of secrets and rumors since its inception. With the release of Mortal Kombat II, fans had many questions regarding the two fighters that appear in the background of The Pit II on the second bridge. The fiery fighter on the right became referred to as "Torch," but was later revealed to be Blaze when he became a playable character in Mortal Kombat: Deadly Alliance.
The green-clad fighter on the left became known as "Hornbuckle" among fans online due to one of the many messages that Jade and Smoke would randomly give before fights. These messages were often hints on how players could find those two characters in the game, but sometimes were just jokes. No one could ever solve what the "Hornbuckle Who?" message meant, so it got attributed to the unknown fighter in the background.
Hornbuckle appears to be a green palette-swap of Liu Kang, but he has never been given an official name by Midway or NetherRealm. He appears again in Mortal Kombat: Shaolin Monks in the same location as before. Several canonical characters in the Mortal Kombat franchise began as rumors or fan theories (i.e. Ermac, Skarlet) and Hornbuckle is one of the last remaining mysteries from the early games in the series. With Tremor appearing in Mortal Kombat X thanks in part to years of fans requesting him, Hornbuckle seems to be next on the list in the hearts of many fans.