From the Super Mario Wiki
Mecha-Koopas (sometimes spelled Mechakoopas), also called Windup Koopas in the New Super Mario Bros. Wii game guide, are one of Bowser's many minions. They are small mechanical versions of Bowser himself, resembling a wind-up toy. They have a wind-up key on their back and their appearances feature several mechanical appendages. They walk in a rhythmical way and must wind themselves up again from time to time in order to keep moving.
Super Mario series
Super Mario World
Mecha-Koopas make a short appearance in Super Mario World, where they are only seen in the last level. In this game, they get paralyzed for a short time when stepped on, so Mario can kick them around, pick them up and throw them. When they get thrown, however, they won't get very far like regular Koopa shells do. They are also not affected by ordinary kicks, as they just freeze, giving the player a chance to throw them somewhere; however, they are vulnerable against the Spin Jump, which turns them into dust.
Super Mario Galaxy
Mecha-Koopas also appear in Super Mario Galaxy with a new look. They are found in Toy Time Galaxy and can breathe flames for fairly long amounts of time. They can only be defeated with a Ground Pound and stunned with a Star Spin. When defeated, they release a coin. In the official Prima Guide, they are called Mecha Bowsers.
New Super Mario Bros. Wii
Mecha-Koopas (also known as Bowser Bots) return in New Super Mario Bros. Wii, where they were found on Airship levels. In this game, they have their appearance from the Mario Party games, and have the same attack pattern as they had in Super Mario World. Unlike in Super Mario Galaxy, they can't breathe fire.
It is shown, that through hacking methods, that Yoshi can eat a Mecha-Koopa. However, he can't jump on one.
Super Mario Galaxy 2
Mecha-Koopas return in Super Mario Galaxy 2, sporting their looks from Super Mario Galaxy. Here, they appear in the Flipsville Galaxy during the mission "Flipsville's New Digs" in the first section of the galaxy, and in the Cosmic Cove Galaxy during the mission "Exploring the Cosmic Cavern" on the last planet. In addition to the Ground Pound, Mario can also use the Spin Drill to defeat the Mecha-Koopas by jumping over them and then drilling into them.
New Super Mario Bros. U
In Hotel Mario, what appear to be Mecha-Koopas reside in Bowser's Seizures Palace Hotel. They are blue in colour, and trundle around in an odd manner. When stomped, they somewhat shrivel up, and cease movement. Later, they do regain movement, though. They can be defeated with a Fireball.
Super Mario RPG: Legend of the Seven Stars
Mario Kart: Super Circuit
Mario Party series
Mario Party 5
In Mario Party 5, the player will fight a group of Mecha-Koopas in the first part of the final battle. They would walk around, occasionally flashing red, then unleashing fiery breath. Jumping on them once will cause them to explode. The player must throw them at each other, or just avoid them all for 60 seconds. Jumping on a Mecha-Koopa while it's breathing fire will hurt the player.
Mario Party 7
In Mario Party 7, Mecha-Koopas appear in the one-player, Bowser mini-game, Tunnel of Lava!. Here, one Mecha-Koopa will eat the key to freedom from Bowser's mini-game area and will retreat into a hole, only to come back a second later with many other Mecha-Koopas. The Mecha-Koopas would then circle the character, who would have to stomp on the correct Mecha-Koopa's head while they circled them before Bowser stomped on the character 30 seconds later. The Mecha Koopas had an attack pattern similar to that found in Mario Party 5, except all the Mecha-Koopas will breathe fire simultaneously.
Mario Party Advance
In Mario Party Advance, a Mecha-Koopa owned the Mushroom Library, and appeared to be an arithmetic genius. The player must complete the quest "Mathemagician!" for the Mecha-Koopa in order to get a Gaddget. The quest consisted of answering three simple math problems; after answering the three questions correctly, the player will be awarded with a Gaddget. The ending says that Mecha-Koopa spends his time creating a new theorem.
Mario Party 9
In Mario Party 9, Mecha-Koopas are given a minor appearance. They only appear in the minigame Mecha Choice, in which they chase the player through the hallway. They also appear to surround the player if he or she chooses the incorrect door. During the first Captain Event on Bowser Station, Heart Star Colony, if there are less than 4 players, Mechakoopas will fill the open spaces, ensuring that there will always be three players for the captain to match.
Mario & Luigi series
Mario & Luigi: Superstar Saga
Smaller versions of Mecha-Koopas make a short appearance in Mario & Luigi: Superstar Saga as conductors to complete circuits of electricity in Bowser's Castle (Unnamed toy mice held the same purpose previously in Woohoo Hooniversity).
Mario & Luigi: Dream Team
Mecha-Koopas (known as Mechakoopas in this game) make their second appearance in the Mario & Luigi series in Mario & Luigi: Dream Team. They appear in Dreamy Neo Bowser Castle as common enemies. They appear in groups and they attack by line up and walk towards the Bros. Mario and Dreamy Luigi has to avoid the Mechakoopas cause they spit fire while they walk towards them. If the Bros. attack a Mechakoopa before battle, they will malfunction and their attack pattern will be irregular. They also attack by surround the Bros. and they have to avoid them by hitting them with hammers. If they are attacked before battle and are in malfunction, they attack in opposite way so Mario has to hit a Mechakoopa in the opposite way.
Mario Power Tennis
In other media
Super Mario World television series
Mecha-Koopas, renamed Mechkoopas, and occasionally called by the generic name Robot, appeared in several episodes throughout the Super Mario World animated series.
Their first appearance was in the episode "Send in the Clown", where a Mechkoopa riding a bicycle acted as the tight-rope walker in Bowser's circus, the "Koopaling Bros. Circus". After the "Koopaling Bros. Circus" was revealed to be an elaborate trap, this Mechkoopa, along with several Chargin' Chucks, began to chase Mario through Neon Castle. This Mechkoopa was eventually defeated by Mario, who had gained the cape ability.
Later in "Send in the Clown", Bowser attempted to defeat Mario by throwing several Mechkoopas at him from the Koopa Clown Car. Mario, after knocking a Mechkoopa unconscious, managed to defeat Bowser by hurling the Mechkoopa at his Koopa Clown Car, causing it to malfunction and crash in a very similar way as Super Mario World.
Mechkoopas next made a small appearance in the "The Night Before Cave Christmas", where several of them attempted to attack Mario and Yoshi, who had broken into Neon Castle. Mario and Yoshi managed to escape these Mechkoopas by using a Feather to transform into Cape Mario and fly away.
The last appearance of Mechkoopas in the Super Mario World TV series was in the show's final episode, "Mama Luigi". Here, Bowser sent a brigade of Mechkoopas after Mario and Luigi as the two explored Bowser's throne room looking for Yoshi. These Mechkoopas, after chasing Mario and Luigi, were defeated when Yoshi simply devoured them.
Nintendo Adventure Books
In Flown the Koopa, if Mario and Luigi run into Bowser in the Valley of the Koopas, he will sic four Mecha-Koopas he had hidden in the trash can he was using as a chair on the two. In one possible scenario, Luigi will smash one of the Mecha-Koopas with his wrench, and make the others destroy themselves (by pressing the sports channel button) after taking their remote from Bowser. In the second scenario, the Mecha-Koopas will knock the Mario Bros. out with their telescoping robotic arms, then turn on Bowser, knocking him out as well. The Mecha-Koopas then wander off, intent on enacting their own world domination schemes.
Super Mario Adventures
In the Super Mario Adventures comic, the Koopalings, after having captured Mario by chance, used two Mecha-Koopas to send a message to Luigi, Toad and Yoshi. Either they exchange Princess Toadstool for Mario, or Mario will be killed, after saying this, the Mecha-Koopas symbolically burnt a Mario Doll with the flamethrowers in their mouths. Luigi then said, "That's Blackmail!". Luigi, with help from Friendly Floyd, managed to trick the two Mecha-Koopas by making them take him to the Koopalings instead of Princess Toadstool.
Names in other languages