One of my father’s (and therefore my) favorite cartoons was Underdog.

Launched in 1964, Underdog was the secret identity of Shoeshine Boy. Though he didn’t possess  any of the powers of today’s glistening, branded superheroes, what Underdog lacked in strength and speed he made up for in grit. And love. Specifically, for girlfriend Sweet Polly Purebread, a name dad found subversively clever, like the show. Underdog could rise to any challenge when his girl was in peril.

No plane, nor bird, nor even frog! the theme song jingled, as our hero smashes into a brick wall, ‘It’s just little old me, Underdog.’ 

Roberta Vinci could have worn Underdog’s U cape to the semifinals of today’s U.S. Open.

The 32-year-old Italian had never made it to a semifinal at a Grand Slam event in her career. And she was to face Serena Williams, who was marching to history. Williams was seeking her 21st Grand Slam title, tying her for the most in the modern era.

Williams is the Tiger Woods of tennis. Athletic. Photogenic. A game-changer shoulders above peers. Like Tom Brady, Williams’ commercials seem to punctuate her games.

Analysts predicted Williams would make quick work of Vinci, whose odds of beating the champ, according to Vegas, were 300-to-1.

Even Vinci, a doubles player by career, began to doubt. She had never managed five games in a set against Williams, whose thighs each are about the width of Vinci’s entirety. Vinci bought a plane ticket back home to Italy for Saturday.

Analysts didn’t help. That gasbag John McEnroe mused aloud whether Steffi Graf, whose record Williams would surely be tying, would show up in New York to personally give Williams the trophy and pass the mantel.

And the show went according to script through much of the match. Williams took the first set easily. When she bored and dropped the second, she began what has become her trademark: working up the crowd. In the third and deciding set, she began to fist pump, clench, whip the audience, which was getting frenzied. On one brilliant shot, she can be seen clearly shouting, either to herself or Vinci, “yes, bitch, yes!” The crowd began to chant. Drake, the celebrity rapper who was in the Williams’ family reserved box seating, stood up and began to applaud.

As Dad would have noted, Sweet Polly Purebread was on the tracks.

But never underestimate a badass beagle.

When the crowd went rabid at Serena’s screams and Drake’s one-man wave, Vinci rested her racket on the asphalt, looked about, shook her head at the thunder.

And smiled. She would later admit she never expected to be there, and decided she was going to enjoy being at a Grand Slam. Center Court, no less. Why not go down swinging?

Williams continued to bomb serves, some of them 126 mph, unheard of in the women’s game (Vinci hits 90 mph on a good day). But with every thunderbolt, there came a steady echo: a shot back. Wham. Return. Blast. Return. Cannon fire. Return. After winning a rally that would become emblematic of her day, Vinci gave her own Bronx cheer. She raised her arms and looked defiantly at the crowd to say, ‘I am here, too.’ After the rally, Williams bent over the net, gasping for air. She would never recover.

Analysts would later rank Vinci’s win as one of the five greatest upsets in sports history. Arguable. But this is not: When she took the microphone after the win, a tearful Vinci apologized to the crowd for beating the toast of New York.

But Vinci became so much more: a life lesson. Never underestimate an underdog. Especially when Sweet Polly’s tied to the tracks.