"I Thought I Lost You" is an upbeat Heartland tune that plays during the end credits, and is performed by the two main actors. Even people who don't like Miley Cyrus love it, and it also showed that 32 years after Grease and Saturday Night Fever, John Travolta still had impressive pipes.
"Barking at the Moon" by Jenny Lewis, which plays over the montage of Bolt learning to be a real dog as he, Mittens, and Rhino travel to Hollywood.
Catharsis Factor: Penny's mom decking the insensitive agent after he callously insists they should use Penny's life-threatening injuries for publicity.
Common Knowledge: Bolt's owner is assumed to be named Penny. That's just the name of the character she plays in the Show Within a Show, and her real name is never stated (though her name is given as Penny in the credits). Though her never being referred to by any other name over the course of the film implies she's The Danza. There's also the fact that Bolt was Penny's pet before being on the show (given the scene of Penny adopting him that opens the film also shows Penny's actual mother), and since Bolt recognizes Penny as Penny, the Enforced Method Acting would dictate that's her actual name.
Mindy, the studio executive, is liked for being a Reasonable Authority Figure who doesn't talk down to Penny.
Fanon: It is widely believed that Penny's actress is also named Penny, if only because no human refers to her by name outside the show (her mother calls her by endearments, and her agent calls her "My Little Superstar") and that her last name is "Forrester".
Disney would later acquire another property featuring a Bolt with a destructive voice.
The Lion Guard gives us yet another animal character with a powerful shout. Only this time, it's for real with him.
Iwájú, a future Walt Disney Animation Studios production, has elements that at least superficially resemble Penny and Bolt's fictional show; The young female protagonist is given a pet (a lizard rather than a dog) that has been enhanced with powerful abilities by her father and faces a threatening villain who intends to capture her because he wants information from the father that would make him more dangerous and powerful.
Hollywood Homely: Mittens is scrawny and has messy fur, but isn't exactly ugly. However, she considers herself not cute enough to be adopted, and when she tries to beg for food, she gets a frying pan thrown at her.
Jerkass Woobie: Mittens. Getting declawed and abandoned by her family turned her into a selfish cynic with deep-seeded trust issues.
Love to Hate: Penny's agent is a walking pile of obnoxious superficiality, glibly talking down to Penny while barely masking his self-centered behavior. Which makes his comeuppance at the hands of Penny's mom oh so satisfying.
Narm Charm: The glimpses of the Bolt TV show are a parody of cliche Hollywood action. But the cliches are done so well, they could work as their own movie.
The huge fire that threatens to destroy the building where the show is filmed at the climax. Seeing Penny and Bolt nearly dying in it is both frightening and saddening.
One deleted scene features Bolt being violently beaten up by a bunch of big aggressive-looking dogs. It's a testament to the abilities of the story artists how horrifying some simple single-panel drawings can be.
Bolt dangling Mittens over traffic. He hasn't realized that he's a normal dog at this point, so he's oblivious that he's putting Mittens in real danger. Mittens is unable to convince him otherwise, and she's forced to play along with him so she doesn't fall.
The studio catching fire with Penny trapped inside. It doesn't help that the scene is an accident waiting to happen because it's set up with numerous fire hazards. With child labor laws and OSHA (especially after what happened on the set of Twilight Zone: The Movie), such a scenario should be unthinkable in real life.
They Wasted a Perfectly Good Character: The actors playing Penny's dad and Calico. They spend their screentime almost exclusively in-character, although Calico's can be spotted out of character and barely in-shot during the studio fire, so their relationship with Penny, if any, is unknown.
They Wasted a Perfectly Good Plot: The hugely fun opening action sequence of the Bolt TV show (along with the fact that it upstaged the entire movie) had a lot of people believing that Bolt would've been a lot better as a high-octane action comedy instead. Not helping is the fact that the video game based on the movie is an action platformer that has its plot take place within the in-universe TV show.
Trans Audience Interpretation: Bolt is unwittingly putting on an act for the vast majority of his life, only to realize he's acting and spends the film learning to be his true self with a feeling of pure, unbridled elation. Naturally, transgender people latched on and related to Bolt's journey of self-discovery.
Ugly Cute: Mittens, to a certain degree. She's a skinny cat humans would look on as a stray, after all. Surprisingly, it is also deconstructed: Since she's not cute in a conventional way, because she's half-starved from being declawed and unable to hunt, humans just tend to scare her away instead of giving her some food, and she's aware that the possibilities of being adopted after falling into a pound are extremely limited for her.
Penny and Bolt take a selfie with a Polaroid camera.
In a meta sense, Penny is voiced by Miley Cyrus, right at the height of Hannah Montana's popularity. Chloë Moretz originally voiced Penny and completed all of her lines, but Cyrus re-recorded most of Moretz's performance.
Another, more subtle example is in scenes that briefly feature period-correct welcome signs for Ohio and Missouri. These signs have since been replaced with updated designs.
What Do You Mean, It's for Kids?: Not so much the final movie itself, despite some slightly dark themes with Mitten's backstory and Penny's agent, but the original version of the movie, American Dog, would have featured elements such as a sexy Parent Service waitress, extremely liberal firearms use, and an undead, radioactive Girl Scout serial killer who constantly stalks the protagonists. It's no wonder that it was called out for precisely this trope by test audiences and producers, and ultimately retooled into the much tamer Bolt.
Win Back the Crowd: Bolt's decent box office returns and good reviews by critics heralded Disney animation's return to glory in the early 2010s. It's nowadays seen as the beginning of the Disney Revival.
Bolt. After discovering he is not really a super dog, he looks so dejected after realizing most of his life was a lie. Even so he still believes that his love with Penny was real. While that is certainly true, he saw her again at the worst time, her hugging his replacement during filming.
Mittens. After being declawed and abandoned by her human family, she had to live most of her life as a stray cat who threatened the pigeons in order to survive. This event has given her a rather cynical outlook on everything until Bolt rescues her from the animal shelter.
The Video Game
Complete Monster: Dr. Calico is a maniacal terrorist with goals to dominate the world through technology and nuclear superiority. Kidnapping Penny's scientist father to force him into servitude, Calico tries to take Penny herself hostage to further his compliance before simply trying to kill the girl and her superpowered dog Bolt for being nuisances. When his Kill Sat weapon is completed, Calico plans to annihilate every nuclear weapon in the world except his own so he will have ultimate power, but not before he hopes to test his new weapon by destroying Penny's hometown then eliminating her father. Even when beaten, Calico enables his escape by launching his entire nuclear arsenal at random targets to distract Bolt, uncaring of the lives that will be lost if they strike.