The idea of an animal speaking to a person is as old as written language, but when sci-fi authors do it, they add a bit of extra context. Talking animals are integral to science fiction, whether they're a science experiment, an alien in the guise of a normal creature, or a person in an animal's body.
Outside the traditional Disney cartoons in which they're the dominant species, talking animals can be heroes, villains, or anything in between. Just about every species a person could imagine has gotten their moment to speak their mind, but some talkative creatures are more memorable than others.
Rocket Raccoon - Guardians of the Galaxy
From a place of relative obscurity in the deeper vaults of Marvel Comics to fan-favorite status in the biggest media empire of all time, Rocket has taken off. Rocket was once an ordinary non-sapient creature, but after years of unethical experimentation, he was transformed into one of the deadliest mercenaries in the galaxy. He's utterly convinced of his skill and his one-of-a-kind supremacy. He doesn't even know what a raccoon is. Rocket immediately stood out among the Guardians when he made his on-screen debut in 2014. Eight years later, he remains one of the most prominent faces of the entire cinematic universe. When it comes to well-known characters, it's tough to get bigger than Rocket Raccoon.
Klaus Heisler - American Dad
Though it isn't the biggest show on TV, Seth MacFarlane's second animated sitcom is one of the longest-running cartoons airing today. The show was recently given its orders for the 20th and 21st seasons, to premiere over the next two years. If the show ends there, it'll have a perfectly respectable 18-year run, but it's not likely to stop. Klaus is the Smith family's pet, but he's also one of the most prominent talking animals in modern TV history. Unlike Family Guy's Brian the Dog, Klaus's English-speaking skills are explained by the narrative with a distinct sci-fi edge. Klaus was once a human man, an East German ski-jumper who seemed destined to take home the gold in the 1986 Olympics. East Germany was a communist state and the 86 Olympics were basically the Cold War's sports section, so the CIA couldn't let Klaus win. To defeat him, they put his brain in a goldfish and dropped him in a frozen lake. He survived and eventually wound up in the Smith household, where he has remained for almost two decades.
Frank the Pug - Men in Black
A one-off gag in the first MIB who was upgraded to full sidekick status in the sequel, Frank is one of the most memorable side characters in the trilogy. Frank is an alien who has taken the guise of a pug to live comfortably on Earth. He's approached by Agents Kay and J for information in the first film, and he provides a few of the film's classic jokes. He became a fan favorite right away for his hilarious voice and charming appearance. His upgraded role in the sequel was a mixed bag. He still has plenty of funny lines, but the character wasn't cut out for such a big role. In the sci-fi noir structure of the first film, he's a perfect take on the classic shady informant character. He's a hedonist who drinks and smokes with his alien friends, and he gets to deliver several of the film's weirdest lines. Frank may not be a real dog, but he's one of the go-to sci-fi talking animals in the minds of a huge chunk of the movie-going public.
Mojo Jojo - The Powerpuff Girls
One of the greatest cartoon villains of the late 90s was once but a humble chimp. The well-meaning Professor used the lovable monkey as a lab assistant. Though the animal proved to be a bit too hyper to be helpful, the Professor loved him like a son. Unfortunately, when the Professor finally succeeded, the resulting explosion changed him forever. His skin turned green and his brain grew madly out of his skull. After a short time on the street, Mojo Jojo was forever changed. He became cruel and violent and used his enhanced intelligence to terrorize the city of Townsville. Mojo Jojo is a sympathetic figure and a great cartoon villain.
Caesar - Planet of the Apes
In the seminal sci-fi series Planet of the Apes, a minor line explains that the first ape to gain intelligence was called Caesar and his first word was "no." The new trilogy has gone on to depict Caesar's journey from zoo attraction to the leader of the revolution. He's one of the most compelling animals in a live-action film and one of the most important talking animals in sci-fi. Tons of other examples have learned from Caesar's example. Caesar isn't the first, but he is one of the most important animals ever to gain the ability to speak.