Rattrap is a Maximal from the Beast Wars Transformers universe, a demolitions expert with his beast form being a rat. Though he was smaller than the other Transformers, he more than equaled them when it came to firepower, with his expert marksmanship and the aforementioned demolitions expertise. However, in Beast Machines, he lost all of this and was not only the smallest, he had no firepower and thus felt useless and depressed at first.

Rattrap's character was scheming, clever, distrustful of 'outsiders', comically pessimistic, and a bit of a coward, with very much of a 'every man for themselves' attitude. He may also have been claustrophobic. He was often distrustful of various individuals who aided the Maximal cause, specifically Dinobot (a Predacon turncoat), Blackarachnia, and Ravage (a Decepticon turned Predacon agent). Despite his flaws, he formed close relationships with Maximal comrades Rhinox and Cheetor, and eventually forged a romantic relationship with Botanica.

Rattrap's exact point in the Maximal command structure is uncertain; he was said to be second in command in an early episode (Chain of Command), but later appeared to be a subordinate under Rhinox's command.

Rattrap had the comic habit of coming up with nicknames for several of his comrades, including Optimus Primal (Boss Monkey, Optimus Pinhead), Dinobot (Chopper-face, the Irracible Raptor, Dinobutt), Tigatron (the Barbarian), Silverbolt (Bird-Dog), and Depth Charge (Captain Minnow, the tin minnow).

Rattrap is believed to be related to Arcee, the female Autobot from the original Transformers series and the animated film.

Rattrap was among the few characters to appear throughout all three seasons of Beast Wars, and both seasons of its spin-off, Beast Machines. He had three forms; his original form (BW Season One), Transmetal form (BW Seasons Two and Three), and Techno-Organic form (BM).

In the English version, Rattrap spoke with a Brooklyn accent and was voiced by Scott McNeil. In the Japanese version, he was voiced by Kappei Yamaguchi