Fan of Underdog

You got no fear of the underdog. That's why you will not survive.

—Spoon, "The Underdog"

The fan of the Loser Protagonist (or mild equivalent) is almost always oblivious to that character's real troubles and failures. This is more amusing when the idolized character is already established as the show's ditz or Unlucky Everydude. When the idolized character becomes aware of this, it will prompt an embarrassed conversation explaining they're not anything special. And then his friends will chime in, a little too enthusiastically.

Naturally, this only serves to make the fan more enthusiastic. Occasionally the fandom is impressed by this lack of Comedic Sociopathy, making them candidates for Better Than Canon pairings.

See also Even Heroes Have Heroes. Contrast Warts and All. Not to be confused with the fandom of a certain cartoon superhero dog.

Examples of Fan of Underdog include:

Anime and Manga

In Maria Watches Over Us, Kanako looks up to Yumi.
Tamao looks up to "victim-chan" Nagisa in Strawberry Panic, as does Chiyo.
Shinobu Maehara in Love Hina seemed inordinately optimistic of Keitaro compared to other others. It makes a bit more sense if you consider *her* as a LoserProtagonist; many of her problems are feminized versions of the troubles he has.
Hinata Hyuuga in Naruto is pretty much defined by her deep-seated crush on the titular character.
- Supporters of Hinata can also be considered under this trope.
- Ironically, Naruto is a fan of Rock Lee for being an underdog like him, as well.
Tohru Honda from Fruits Basket could be considered a straight take on this, she's easily the cat of the zodiac's biggest fan (this includes Kyo). She's not so much oblivious of his faults as understanding that there are some serious underlying causes. When she heard the legend of the zodiac as it's usually told she explicitly declared the cat her favorite for exactly this reason before she even met him.
One of the results of Yurika Misumaru's similarly obsessive crush on Akito in Martian Successor Nadesico.
When Sora Naegino from Kaleido Star is shunned by almost all the performers and her mentor isn't sure she can make it, her only supporters were two new recruits (Mia and Anna), her stage manager (Ken), the dorms manager (Sarah) and the lead stagehand's daughter (Marion).
Cesilee and Marcus in The Cyantian Chronicles
Pretty much half the cast of Katekyo Hitman Reborn admires Tsuna for unclear or misguided reasons.
In Deadman Wonderland, Senji (AKA Crow) is shown to take a huge liking to Ganta (partly because Ganta defeated him, but that was mostly by a fluke), even though Ganta showed himself as being quite a coward and weakling.

Comic Book

Don Rosa's two Three Caballeros comic stories portray Panchito and José as idolizing hapless Chew Toy Donald Duck, in a nice contrast to all the comical abuse he takes from everybody in Duckburg.
In Identity Crisis, Ralph Dibny recounts how he and his wife Sue met. He and The Flash had shown up at some fancy event and saved everyone there. A-lister Flash had nearly everyone's attention—everyone except Sue, who was immediately interested in B-lister Ralph. Ralph claims that's one of the reasons Sue is so special—despite being surrounded by superheroes with heroic builds and chiseled good looks, she's never had eyes for anyone but Ralph.

Film

Walter from The Muppets is the muppet personification of this trope. He loves The Muppets regardless if they have been out of the loop for 30 years and has an unbridled admiration for them. Case in point: he finds Fozzie Bear genuinely funny.

Literature

Practically the entire relationship between Rincewind and Twoflower in the Discworld novels The Colour of Magic, The Light Fantastic, and Interesting Times. Twoflower is incredibly naive, and a few off-the-cuff bravado remarks by Rincewind have cemented him in Twoflower's eyes as a great wizard, despite the fact that he can do no magic whatsoever and his talents rely entirely on running away from things.

Live Action TV

The Big Brother winner each year is the person at the biggest disadvantage: a transsexual, a Tourette's sufferer, Alex, etc.
- This is most likely related to how the British are famous for supporting the underdog.

Professional Wrestling

Many Jobbers have their own devoted fanbases.

Video Game

In Tales of Symphonia: Dawn of the New World, Marta is this for Emil, in a more romantic way.
In Fire Emblem, if you choose to have them support each other, Rebecca the Archer becomes this towards Lowen the Cavalier; she embellishes his 'daring rescue' of her village knowing full well that she's doing so, simply because she prefers to remember it that way.

Web Comic

Ricky "Turtle" Tuttle in PvP manages to be an even bigger loser than Francis while idolizing him to a fanatic level. He even kills himself by literally jumping off a bridge because he thought Francis would approve.

Western Animation

One episode of Captain Planet had a boy named Jason idolize Wheeler. It would be a stretch to call Wheeler a "loser," but he is usually the least knowledgeable and biggest screw-up of the team.
One episode of Hey Arnold! combines this with Warts and All. The chronically-unlucky geek Eugene discovers his favorite superhero's actor is really a Jerkass and abandons his usual attitude in order to "go bad." Unfortunately, there's a younger kid who looks up to Eugene, and suffers a similar sense of disillusionment at Eugene's change. (In the end, though, both get a happy ending after being rescued from near-death by the previously-nasty actor.)
Milo of Pepper Ann only cheered for the school team when they were on a loosing streak, his mantra regarding sports being "choose to lose." Once they started winning, he quickly lost interest.
X-Men: Evolution portrays Amanda Sefton as one of these, in regards to Kurt "Nightcrawler" Wagner.
In one Tiny Toon Adventures episode, Acme Loo has lost every single football game of the season. Sneezer is the only fan, specifically of Plucky.
The more outspoken, zealous fans of the character Lemongrab of the show Adventure Time tend to be this IRL, as they tend to overlook the painfully obvious fact that the character, though he is downtrodden, is a complete asshole to everybody around him.
Recess had Gus (the underdog, and general Unlucky Everydude of the series) being idolized by a kindergartener who called him "safety man" and believed him to be the coolest of all the older kids on the playground. In a later episode when Gus does become "cool" in the eyes of his peers, the kidergartener is the one who tells him he was more respectable before as "safety man."

Real Life

A general Real Life example in regards to sports. It's not too uncommon a notion that one will, given that their local/favorite team isn't doing well in most situations, cheer for whoever is the comparative underdog. Especially true in professional-level playoffs and collegiate-level rankings.