Mortal Kombat is full of secrets, apparently.

YouTuber YourMKArcadeSource discovered hidden "EJB" menus in the first three Mortal Kombat arcade games that — among other things — unlock a challenging Galaga clone and open up a video of all the game's fatalities playing back to back.

The letters "EJB" are the initials of Ed Boon, creator of the Mortal Kombat series. The menu titles suggest that he's the one who programmed the hidden menus into the arcade games.

Unlocking the menus involves pressing the player one and player two block buttons in a very specific, very complicated sequence. The process for each game is laid out in the video, so give it a watch if you want to do this yourself.

It's not clear if there's a similar menu in the arcade version of Mortal Kombat 4 or any home version of the games. This is still an unexpected discovery, considering that the most recent of the three games is still more than 20 years old.

Have something to add to this story? Share it in the comments.