Dark Block

A Dark Block is a ? Block-impersonating Block enemy, found in the game Mario & Luigi: Dream Team. They appear only in Dream's Deep. Outside battle, they appear stationary until approached. They then appear to "grow" a "face" and move sideways. In battle, they float above Mario. Jumping into them counts down a timer. If the timer doesn't reach zero at the end of the attack, the "face" appears on the Dark Block as it falls on Mario, and may inflict a Dizzy status. Another attack that it uses is floating above Mario, but with spikes and Brick Blocks. If any attack is countered, the Dark Block's "face" appears sad, and the Dark Block's defense lowers. If a Dark Block is defeated, it transforms into an actual ? Block. The ? Block drops a Coin or an Item when hit, then disappears.

Trivia
Dark Blocks are the only enemies in the Mario & Luigi series to not use 2D sprites like most characters, and is instead seen as a 3D render, along with Shiny RoboBowser, the final boss of Mario & Luigi: Paper Jam.