Mortal Kombats I-III are known to have a secret menu that can be entered, by anyone, from the title screen. Mostly filled with location statistics, lead developer Ed Boon put it in to check on the game's performance in the field, but it also has some fun features like showing off all of the fatalities and endings.

All of the codes are entered from the title screen in attract mode, with only the P1 and P2 block buttons (here they're written as P1 and P2). The timing is tight and must be finished before the screen ends: MK2: P1x5, P2x10, P1x2, P2x8, P1x2 MK1: P1x 5, P2x10, P1x2, P2x1, P1x2, P2x3, P1x4 MK3 (also works in Ultimate): P1x5, P2x10, P1x3, P2x1, P1x2, P2x2, P1x3, P2x3

The main link of the post is to the Cutting Room Floor's page on MK2, but there are also pages for MK1 and MK3. Our blog Set Side B did a post on them back in 2022.

The Substack Rings of Saturn is a good place to look for secrets, they use reverse engineering techniques to find undisclosed and undiscovered codes. One recently found, believed to be hitherto unpublished, unlocks (nearly?) all the characters for Dynasty Warriors on Playstation. From Character Select, it is Up, Down, Down, Right, Right, Left, Down, Square, Circle, Up, Up, Triangle.

In Tomodachi Life: Living the Dream, the Marketplace opens for morning business at 5 AM each day. However, the island's shop inventories change at 6 AM. This means, for the one hour between them, you can still buy the previous day's morning food special before it is swapped out.