Big Arm

Big Arm (ビッグアーム) is the final boss of Sonic the Hedgehog 3 and the first boss in the Nintendo 3DS version of Sonic Generations. The Big Arm is a large modified Egg Mobile, that has heavily armed with spikes on its top and two big, mechanical hands, which are able to grab its victim and then slam it against the ground. It has also two small rotors behind to hover forward in the air.

Sonic the Hedgehog 3 & Knuckles
The Big Arm has first appeared in Sonic the Hedgehog 3 and is the last of three bosses fought in the second act of Launch Base Zone. It is also final boss of the standalone Sonic the Hedgehog 3. After defeating the previous two Robotnik's vehicles, the doctor has the last vehicle, which he flies to pick up from the Death Egg. After that moment, the sky changes from bright to the dark one, as Robotnik lands down to the arena and the climatic battle has come. Because it has spikes on the top of the cockpit and wide arms below, the Big Arm has limited space for where it can be attacked. Also with it two big hands, the Big Arm can grab the players, rolling them into a ball and slamming them down. Normally the player's only real chance to attack this boss is when it swoops across the screen. The player must make a well-placed Spin Attack to attack the cockpit–too high and the character will hit the spikes, too low and they will be grabbed by the hands. While playing the standalone Sonic the Hedgehog 3, using the Insta-Shield is an effective tactic for Sonic.

It takes 8 hits at a time to destroy this vehicle, as after that, Big Arm gets destroyed and Eggman with Egg Mobile falls from the arena. The explosions from Big Arm starts affect to Death Egg itself and the arena along with Sonic / Tails gets detached from the space station. The player sees destruction of Death Egg at the background, thus ending the first part of Sonic the Hedgehog 3 and the game then progresses to the end credits.

If Sonic the Hedgehog 3 is locked on to Sonic & Knuckles (in the form of Sonic the Hedgehog 3 & Knuckles), Sonic and Tails does not fight with this boss. However if the player has Knuckles, he will still have to fight this boss vehicle, which has this time EggRobo piloting it. Because the Knuckles' story takes place after Sonic and Tails adventure, the battle will take place to the upper arena at the end of second act. However the scenery doesn't go dark after destroying Egg Robo's first vehicle, but the battle would be more challenging for Knuckles due to his low jumping abilities.

Sonic Generations
The Big Arm makes an appearance in the Nintendo 3DS version of Sonic Generations, as the classic-era boss. The boss fight is similar to Sonic the Hedgehog 3, with new attack patterns. It can now strike from above by punching down on the platform, and rocketing across the arena trying to impale Sonic with the spikes on its head. After half its health is depleted, more spikes emerge from the forearms, making it trickier to attack the cockpit. In phase two, it can also attack from the background and attempt to grab the player.

Sonic the Comic
In Sonic the Comic, Robotnik pilots the machine, here referred to as the "Squeeze Tag Machine", when he invades Sonic's Secret Underground Base in the Emerald Hill Zone. The machine is built so solidly that Sonic cannot damage it. Luckily, he is helped by Knuckles, who cracks the small windscreen with a punch, weakening it enough for Sonic to tear the top of the machine off with a Spin Attack.

Trivia

 * If the Big Arm grabs Super Sonic, the character will lose their rings, and thus lose their Super State. But if it grabs Super/Hyper Knuckles, it will create a Spring sound effect and Super/Hyper Knuckles will not lose any Rings.
 * If a character is in their Super or Hyper form, they will be able to damage the Big Arm when it comes down to sweep across the platform. This can also be done without transforming, requiring a well timed spin dash.
 * When playing Sonic 3 & Knuckles, this boss fight doesn't appear (If playing as Sonic and/or Tails) and the player will move on to Mushroom Hill Zone.
 * In the 3DS version of Sonic Generations, while battling this boss, the music was originally going to be a rock remix of The Doomsday Zone. This remix was only used in E3 2011 version of demo but in Gamescom 2011 demo, it was replaced by a remix of its own theme (the final boss theme) from Sonic the Hedgehog 3.
 * Big Arm is the first boss in Sonic Generations to ever be officially confirmed.
 * This is the only boss from Sonic the Hedgehog 3 to appear in Sonic Generations. Likewise, its Launch Base arena is the only level from Sonic 3 to appear in Generations as both versions take their main levels from its add on.
 * The music here is also the same music as the final boss of Sonic & Knuckles.
 * In the 3DS version of Sonic Generations, there is a glitch where Big Arm will be stuck charging up his punch; He will still follow the player around, and he will play the charging up animation, but he will never bring the punch down, and he is too high to be hit; as shown here and here. The only solution is to exit the battle.
 * While Big Arm hasn't appeared in Archie Comics, Eggman is seen piloting it in the cover for Best of Sonic the Hedgehog Villains hardcover graphic novel.