I was never a big fan of the "Rocky" movies. Built on the dreams of actor-writer Sylvester Stallone, wearing its big heart unabashedly on its sleeve, the first "Rocky" charmed audiences with the image of this big, gentle, slow-witted bruiser with the courtly manners and modest outlook in life who--as the boxing-movie cliché goes--"getsa shot adda tiddle." Stallone captured the way ordinary folk talked and acted in Philadelphia, and he had in particular a feel for how big palookas think--how they're constantly aware that the world looks at them as freakish and grotesque and not a little stupid, how Rocky basically doesn't mind, so long as he has this small space for himself--an apartment, a turtle, not much else. Stallone's able to convince us that this might actually be a reasonable way of living after all, no small achievement.
Then it turns into a huge fairy-tale, and suddenly we're in rah-rah mode: Rocky pummels a beef carcass (must be how Philly cheesesteaks got so tender), runs up the Art Museum's stairs, does a little victory jig to the tune of Bill Conti's "Gonna Fly Now" number (with tremulous violin strings suggesting the thrill of the moment), and we believe this nobody can beat the heavyweight champion of the world. To be fair, Stallone didn't pluck the idea for his screenplay out of thin air; he'd been inspired by the career of Chuck Wepner, a relative unknown who in 1975 had been given a chance to fight Muhammad Ali for the title. Wepner surprised everyone by lasting far longer than the expected three or four rounds, even knocking Ali down on the ninth (the only fighter to have knocked Ali down while he was the heavyweight champion); he lost to Ali on the fifteenth by a TKO. You can see the basis for the story here, though Stallone couldn't resist polishing and even whitewashing the facts a little--Wepner had been a longtime professional and had fought noted boxers such as George Foreman and Sonny Liston before being given his title shot, and he was no innocent (in 1986 he was arrested for cocaine possession).