Super Mario series
Super Mario Bros. / Super Mario Bros.: The Lost Levels
Super Mario Bros. 2
In Super Mario Bros. 2, the tip of the cap had been changed to black instead of its usual green. This happened for the Mario Cap as well. However, after this game, the Luigi Cap reverted to having a green tip.
Super Mario 64 DS
In Super Mario 64 DS, Luigi's Cap was used to shape-shift into Luigi if the player was either Mario, Wario, or Yoshi. In the same game, Luigi is affected in the same way as Mario and Wario if his cap is lost. Luigi's defense and attack sharply decline while his cap is absent from his head. If the player gets the cap back, Luigi's attack and defense revert to normal. Until Luigi is unlocked, it only appears in Big Boo's Haunt, on any star except the first one. If the player obtains a Power Flower while wearing the cap, they will turn into Vanish Luigi. If he loses his cap and gains a star from another level, Luigi can simply talk to Toad (who will have found and be wearing Luigi's Cap).
Super Mario 3D Land / Super Mario 3D World / Super Mario 3D World + Bowser's Fury
In Super Mario 3D Land and Super Mario 3D World, Luigi, like his brother, loses his cap in his Small form. However, in the former game, once the player has 1110 lives, his regular form loses his cap instead.
Super Mario Odyssey
The Luigi Cap can be obtained for Mario to wear in Super Mario Odyssey. It can either be purchased from a Crazy Cap store or obtained through scanning a Luigi amiibo (the latter also unlocks Luigi's costume).
Mario Kart series
Mario & Luigi series
In Mario & Luigi: Superstar Saga, Mario & Luigi: Partners in Time, and Mario & Luigi: Bowser's Inside Story, the "L" on the Luigi Cap is black. The Mario Cap was changed in the same way. From Mario & Luigi: Dream Team onward, they are the usual green and red.
Super Smash Bros. series
Super Paper Mario
Mario Sports Superstars
Mario + Rabbids Kingdom Battle
Names in other languages