L Block

L Blocks are a type of Block exclusive to the Mario & Luigi series. They are basically identical to ? Blocks, though only Luigi or Baby Luigi can activate them. M Blocks are similar to these blocks, however, M Blocks can only be activated by Mario or Baby Mario. In Mario & Luigi: Bowser's Inside Story, they are mainly used for mini-games to earn Attack Pieces. They may also contain items for the Mario Bros. to collect. In Mario and Luigi: Superstar Saga they are often used to solve puzzles, while in Mario and Luigi: Partners in Time they usually contain coins or items.

L Blocks, along with the M and W Blocks, were originally going to appear in Super Mario 64 DS and contained L Caps, but they were removed. The blocks can still be found in the beta test level.