Brain is a dog on the cartoon show Inspector Gadget. He is the pet of Penny, the Inspector's niece. Brain is unusually intelligent for a dog in that he is sometimes anthropomorphic. This may explain his name.
Brain often walks upright, and communicates with Penny through a device built into his collar. Brain can communicate with humans using his voice, but has some difficulty with pronunciation, despite this. Aside from speaking in a low gruff voice, he tends to interject most words with the letter "R" similar to the way other cartoon dogs, such as Scooby-Doo and Astro from The Jetsons, do. How much the humans in the show understand him is debatable, since he mostly uses pantomime to communicate.
Brain typically follows Gadget on his missions using various disguises. Gadget never recognizes him and more often than not takes him for the prime suspect for committing the crime he is supposedly investigating.
He was voiced in the television series by Frank Welker, who debuted voicing Fred in Scooby-Doo (who would also ironically go on to voice Scooby-Doo using a voice similar to his Brain voice). In Gadget, Welker also voiced villain Dr. Claw and MAD Cat.
Brain is called Sultán in the Spanish version, Sabihondo (Spanish for know-it-all) in the Latin American Spanish dub, and Finot in the French and first Italian version. Bravo in second Italian version.
In the spinoff Gadget and the Gadgetinis, Brain had retired from crime-fighting, after being traumatized by anything with Gadget's face. The end-credits showed sketches of Penny on her bicycle visiting Brain who now lives in a riverside house. The pair enjoy an emotional reunion. He does appear in episode 36, No Brainer, when Gadget is kidnapped and Brain's scent is needed to rescue him. Penny constructs a new collar for Brain that allows him to talk clearly and understandable to humans.
Brain appeared as a non-anthropomorphic beagle in the 1999 film and its sequel. During the closing credits of the first movie, Penny invents a collar which enables Brain to speak and understand the human language. His speaking voice in the first film was provided by Don Adams (who played Inspector Gadget in the original cartoon series) and by Jeff Bennett in the sequel.
Frank Welker reprised his role as Brain in a segment of the Robot Chicken episode "Adoption's an Option." In the segment, after Inspector Gadget was chasing him and Penny (due to having Cyberdyne in him), Brain helped Penny crush Inspector Gadget in reminiscence of the Terminator films.