There is a secret code in Donkey Kong 64 that will only play a funny noise, and nothing else. Standing next to a torch in K. Lumsy's room and pressing C-Up, D-Down, C-Left, D-Right, C-Down, D-Up, C-Right, D-Left will make a burp sound... and that's it. There are no other effects.

In Paper Mario: The Thousand-Year Door, each Shine Sprite can be collected twice because the icon of it appearing is not merely visual, but literally another Shine Sprite. This provides a cautionary tale to developers about never implementing a visual effect as the object itself.

In the "Waltz of the Boos" theme from Super Mario Galaxy, the pizzicato arpeggio in the beginning and throughout the song spells out "DEADEAD DEADEAD". Whether the usage of the sequence "DEAD" for a ghostly theme is deliberate or merely a fitting coincidence is unknown.