Quick Answer: It may seem like the only thing required of onscreen dogs is to continue to be cute and lovable on screen, and while that may be the case, Hollywood history has shown that there is always room for a screen-stealing dog performance. And at least in these cases, the adorableness is as much a vehicle for the film's central themes as it an opportunity to create a theater wide collective “Awww!”

For many decades, audiences have never tired of watching dogs perform the big and small screen. As we’ve seen with the advent of the Internet age, people are willing to spend hours of their time watching cute dog videos, and we’ve known since classics such as Old Yeller (1957) and Airbud (1997) that people have a huge capacity to sympathize with canine characters. Whole niche genres have been invented by such films, like the a-boy-and-his-dog genre and the movie starring animals as star athletes genre. But which performances stand out as effective dramatic tools, as opposed to gimmicky injections of adorableness? Can a dog deliver something like a masterful performance?

Probably not, but due to the assistance of trainers and directors, these dogs fit effortlessly into the framework of the films and TV shows in which they appear. As we're trying to understand what makes a canine performance special, we're excluding any instances in which a dog has been dubbed over or animated. Only purebred performances here.

Uggie (Jack) from The Artist (2011)

Uggie was a Jack Russell terrier who found widespread adoration and fame for his portrayal of the unyieldingly loyal pet of George Valentin in The Artist. Uggie has on screen charm that few human actors possess, as well as an uncanny ability to draw the attention back onto himself. He embodies the emotional drive of the narrative, blushing when George and his love interest kiss, rushing to alert the authorities when his owner is in danger, and barking at or biting anyone who intends harm upon his owner. Uggie reflects what we as audiences want to see in the movie, as well as in ourselves. He is small and scrappy, and he fights as best as he can against steep odds to find happiness for his owner, as well as himself.

Moose and Enzo (Eddie) from Frasier (1993-2004)

Another career canine actor, Moose played the role of Eddie, a dog who seems to always end up at the center of Frasier’s frustration. A different character type to Uggie in The Artist, Eddie seems to consistently embed irritation in Frasier’s day-to-day life. He’ll produce a litter of adorable but needy puppies with a neighbor's dog; he stares incessantly at an awkward and uncomfortable Frasier; and time after time his entrance onscreen comes as the punchline of a joke that makes the live audience loses their mind. It’s difficult not to love the adorable Eddie, whose air of utter detachment only endears him further. From the eighth season onwards, Moose's son Enzo replaced his aging father in the role of Eddie, and the son continued his father's iconic skill for staring straight through Frasier's soul. 

Spike (Old Yeller) from Old Yeller

Perhaps the most outwardly dramatic role on this list, Spike put in a classic performance as Old Yeller in the 1957 adaptation of the Fred Gipson novel. Spike takes on a similar role to that of Uggie in The Artist. He is fiercely protective of his adopted family and time after time puts himself in the line of danger to prevent harm from falling on them. His fate finally catches up to his self-sacrificing streak, as he contracts rabies while defending his family from a wolf. Old Yeller is a heart-wrenching tale of growing into adulthood made much more effective due to a stellar performance by Spike.

22 different dogs in Marley and Me (2008)

Marley and Me is an example of a film that effectively capitalized upon the dog-lover movie-going market. Despite receiving a majority of average reviews from critics, Marley and Me was a box office hit, thanks in no small part to the litany of dogs who played Marley over the course of the film. As the story followed Marley from his puppy days up until his final hours, a host of dogs were needed to fulfill the role.

As is the trend with the dog-centred films on this list, Marley fulfills a thematic need to show the growth of the other characters in the film. The film is fuelled by their reactions to Marley’s misadventures. Critics have commented that the film isn't flush with rich characters or compelling ideas, but the canine performances are managed in such a way that we feel that we are growing up with Marley. You might call Marley and Me the Boyhood (2014) of dog films, due to the way it accelerates time in order to jolt our emotions into seeing the bigger picture of a person or animal's life. (Marley and Me didn't commit to waiting for one canine actor to age in real time, though.)

[SPOILERS] The time-accelerating technique makes the finale when Marley dies peacefully so much more heartbreaking. It calls on the viewer's own experiences of seeing their own dogs grow up and pass away. Marley and Me achieves at least in a minor sense what any powerful dramatic film attempts to do: using what's onscreen to make the viewer look inward. Because we see an abridged version of Marley's life as he grows up and eventually dies, we are taken through a journey of dog ownership that transcends any of the individual day-to-day scenes on their own.

Pal (Lassie) from Lassie Come Home (1943)

Despite starting as a stand-in for the original star of the tear jerking 1943 classic Lassie Come Home, Pal showed such fearlessness during a particularly dangerous shoot that he convinced the producers he was the dog for the role. The film became a financial and cultural hit, leading to a series of sequals and remakes. Pal went on to star in seven films and a television show, in what has been called "the most spectacular canine career in film history" by The Saturday Evening Post.

Pal became so trusted in the role of Lassie that when casting for the role of the boy in the TV series, Pal was left with the decision of choosing which of the narrowed down list of three candidates he enjoyed filming with the most. Pal was revered in directing circles and was known to be intensely professional and a rapid learner, rarely requiring more than one take. While the litany of content that followed from his onscreen debut didn't capture the magic of the original, his performance in Lassy Come Home is probably as close to a showstopping performance as possible from a dog.

Beethoven (Beethoven) from Beethoven (1992)

Beethoven is an unapologetically corny film with some of the cheesiest acting and dialogue ever seen on screen. But there's space for cheese in cinema, especially family films, and at the very least, Beethoven is an endearing homage to the less-than-perfect dogs out there. Beethoven moves seamlessly between hero and nuisance, at once saving his owner's daughter from drowning, at other times tracking unbelievable amounts of mud all over the house. The dog is a slobbering, lovable mess with little to no regard for household rules but an unwavering sense of loyalty to his owners. The story shows Beethoven's transition from troublemaker to lifesaver, when his seemingly obnoxious outbursts turn out to be attempts at protecting his family.

Chris the dog's performance as Beethoven revels in slapstick, over-the-top physical comedy. Whether he's running across a well-set dinner table or leaving a mountain of mud on his owner's bed, Chris goes big, and he sells it.

It may seem like the only thing required of these dogs is to continue to be cute and lovable on screen, and while that may be the case, Hollywood history has shown that there is always a room for a screen-stealing dog performance. At least in these cases, the adorableness is as much a vehicle for the film's central themes as it an opportunity to create a theater wide collective “Awww!”