M Block
From the Super Mario Wiki
A red M Block found in the Mario & Luigi sub-series serves the same function as a ? Block. This type of block can only be activated by Mario and Baby Mario.
M Blocks also appear in Yoshi's Island DS. In this game, Yoshi must be carrying Baby Mario to see them and hit them. Also, some remain invisible even with Baby Mario; these blocks must be hit by Yoshi (with Baby Mario) to appear. The stage Hit the M Blocks! is named after them.
| Blocks |
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| ! Block | ? Block | ♪ Block | 4-Bros. Random Block | Arrow Block | Aurora Block | Bonus Block | Brick Block | Bros. Block | Coin Block | Command Block | Control Block | Dice Block | Dotted Line Block | Drop Block | Egg Block | Event Block | Expansion Block | Giant ? Block | Giant ! Block | Grab Block | Heart Block | Hidden Block | Hint Block | Ice Block | L Block | Laser Block | M Block | Marshmallow Block | Metal Block | Minus Block | Mushroom Block | Perry Block | Pink Block | Plus Block | POW Block | Pushing Block | Rally Block | Random Block | Rock Block | Save Block | Shine Block | Simu-Block | Spin Block | Star Block | Stone Block | Super Block | Triangular Block | Turning Block | Used Block | Warp Block | Wooden Block | Yellow Block | Yoshi Block |

