A Robot Drone with a Mouser-like design appears in the episode, "I Think His Name is Baxter Stockman", as part of an advanced combat suit that is separated by Leonardo's katana and then develops a life of its own. Later Baxter Stockman builds his own version of the Mousers, with the same appearance and purpose as in the Mirage comics.
The Mousers officially appear in the episode "Mousers Attack!" This time they behave more like their previous incarnations, burrowing underground to steal valuable items for their master. However, their name is now an acronym for "Mobile Offensive Underground Search Excavation and Retrieval Sentries", indicating that dealing with mice and rats was not their original purpose. Ironically, their vocals sound like cat meows. They attack their targets when said targets are sprayed. At first, Leonardo and Raphael had trouble with the M.O.U.S.E.R.S. Fortunately, Donatello tells them that the spray wears off gradually and if someone got sprayed, it gives off a strong signal. As Baxter attempts to spray all four of them, he and Dogpound become the M.O.U.S.E.R.S.' targets instead after Raphael slices the spray.
In Booyaka-Showdown, Part 1, they appear with the brainwashed Kirby O'Neil when Karai captures April and hands her over to the Kraang. they were used to send a message to Splinter to come and face Shredder in his lair. This was the first time out of all of their appearances that they appeared without their creator, Baxter Stockman. one of them then appears at the shredder's hideout as it projects a hologram of April to lure splinter into his trap. upon discovering this, splinter destroys it using a Shuriken.
Their first appearance in the 2nd season is in Mikey Gets Shellacne, where they help Baxter Stockman fight the turtles. They end up being electrocuted and destroyed by Rahzar who sticks his hand into a nearby outlet in the T.C.R.I. building after he was tricked by Mikey and has was double mutated after falling into a vat of Mutagen.
They then make a cameo in Target: April O'Neil, where they act as a projection screen that the shredder uses to speak to Karai through as he's still in Japan. He then informs her that he has found out about her recent failure of defeating the turtles as well as the fact that she disobeyed him and his orders. Karai then states that the Kraang have made improvements to the Foot-Bots who she blames for the turtles escaping. The shredder then interrupts her and informs her to not to have any dealings with the Kraang until he returns. He then warns her that if she does disobey him again the consequences will be severe before he signs off.
They then made their first appearance in the third season in Return to New York, where they were seen patrolling the subway with the Kraang. they are then seen in the sewers trying to attack a deranged splinter. luckily the turtles show up and take them all out as they try to restrain and help their sensei. unfortunately one mouser survives and calls for backup; this results in Foot-Bots showing up. despite the turtles best efforts, splinter ends up getting captured and taken to the shredder.
They reappeared again in The Fourfold Trap where they were used by Karai to lure out the turtles.Baxter loaned them to her and programed some holograms of April, Mr. Murakami and the Turtles. also the Helmet that Karai used on Donnie in his trap was actually the top part of a M.O.U.S.E.R.'s head.
In the fourth season, they made a brief appearance in Broken Foot as they projected a video of a factory that the Shredder has been using to produce a new version of Footbots that resemble Chrome Dome which Karai and Shinigami plan on locating so they can destroy it and therefore cripple the Shredder's army who will be diminished greatly.
A Mouser made an appearance in Tale of Tiger Claw where it acted as a hologram for Super Shredder who used it to speak to Tiger Claw before signing off. It then made a appearance at the end of episode where it acted as part of a trap for Alopex and trapped her in a laser cage. when the turtles showed up to rescue Alopex, it was destroyed by April who impaled it through it's head with a sword.
- "Mousers Attack!"
- "Baxter's Gambit"
- "Showdown, Part 1"
- "Mikey Gets Shellacne"
- "Target: April O'Neil" (Cameo)
- "Return to New York"
- "The Fourfold Trap"
- "Broken Foot"
- "Tale of Tiger Claw"
Description and abilities
Standard Mouser robots are of the approximate size and shape of a turkey. They have a single eye and two enormous, hardened steel toothed jaws that can bite through concrete, brick and steel with ease. In addition, the Mousers are with their gripping toes able to climb walls, and have a body cavity, with which they can transport swallowed material or objects.
Standard Mousers only have a low intelligence and no independent thinking skills, they are basically drones and usually controlled by a central computer station or simply a remote control.
- The Mousers make cat sounds and screeches.