An Eggman Mark (エッグマンマーク,Egguman Māku?), also simply known as the Robotnik monitor, is a "power-down" Item Box that appears in earlier games of the Sonic the Hedgehog series. While designed as an monitor power-up, it is actually a disguise hazard that can hamper the player.
The Eggman Mark is known to have the smiling face of Dr. Eggman on its monitor's screen. By breaking its monitor, it will cause damage to the player, resulting in the loss of either a shield, Rings or even a life, should the player not have any Rings at the time. However, it does not have any effect if the player is invincible or in a Super State.
Sonic the Hedgehog 2
The first, official appearance of the Eggman Mark is Sonic the Hedgehog 2, where these objects can only be found in the 2 Player mode of the game. It can be seen if the monitor items are randomized. By breaking an Eggman Mark, the player loses his/her shield/rings or even a life as if attacked by a Badnik, which could strongly affect the outcome of the race. In the 2013 re-release for mobile platforms, these monitors may also occasionally appear in character-specific paths in single-player.
Sonic the Hedgehog 3 & Knuckles
Robotnik monitors are seen in the game Sonic the Hedgehog 3 and its add-on continuation Sonic & Knuckles. In these games, Robotnik monitors are more rare, but are set in inconsistent places. The first Eggman monitor can be found in an underwater section of Hydrocity Zone Act 2 in a corner on top of spikes. The next two Robotnik monitors can be found in a cavern of IceCap Zone Act 2, where monitors are normally frozen and the player should avoid breaking them. Another three Robotnik monitors are found in the second act of Launch Base Zone, where two are set at the foot of a tunnel and a single one in a corner with a Super Ring monitor, where the player pops out the water pipe.
The next Eggman Mark is found in Mushroom Hill Zone, which is right next to a Super Ring monitor, which hides a spring beneath it. Next two are found in the second act of Lava Reef Zone, where these monitors are set at the foot of a blocked, hidden entrance, where only Knuckles can access them. The last one can be found in the second act of Death Egg Zone, which is near an anti-gravity switch and right next to a Super Ring monitor.
Monitors featuring the face of Dr. Robotnik are seen in Sonic Blast. However these monitor items act much different, as the player simply doesn't earn anything by breaking the monitor with this item. These items can also pop out from monitors with question marks, which randomly choose any of eight monitor items of the game.
One of the unused monitor items in the original Sonic the Hedgehog are Robotnik monitors which, by hacking the game, do nothing after breaking it. The Robotnik item icon is different compared to ones in later games. In the 2013 re-release of original Sonic the Hedgehog, it could be placed by using the game's Debug Mode and it functions like it later did in Sonic the Hedgehog 2 and Sonic the Hedgehog 3 & Knuckles.