- [from the opening scene of the pilot episode, "Safe Waif", also used as the show's prologue]
- Narrator: One of the city's most humble and lovable characters was... Shoeshine Boy.
- Shoeshine Boy: [finishes shining a man's shoes] All finished, sir.
- Man: [gives Shoeshine Boy a silver coin] Thanks, Shoeshine Boy, you're humble and lovable.
- Shoeshine Boy: Bless you, sir.
- [bites coin]
- Narrator: Little did anyone know that whenever there was a call for help...
- Woman: Help! Help-Help!
- [Shoeshine Boy's ears perk up in surprise]
- Narrator: Shoeshine Boy became, in real life...
- [Shoeshine Boy runs into a telephone booth, which explodes, and he emerges as...]
- Narrator: Underdog!
- Lyrics to Underdog theme: When criminals in this world appear / And break the laws that they should fear / And frighten all who see or hear / The cry goes up both far and near / For Underdog! Underdog! Underdog! Underdog! / Speed of lightning, roar of thunder / Fighting all who rob or plunder / Underdog. Underdog! When in this world the headlines read of those whose hearts are filled with greed who rob and steal from those who need to right this wrong with blinding speed goes Underdog! Underdog! Underdog! Underdog! Speed of lightning, roar of thunder, fighting all who rob or plunder Underdog. Underdog!
- [repeated line]
- Underdog: [whenever something goes wrong] I am a hero who never fails. / I can't be bothered with such details.
- Announcer: [At the end of each show] Looks like this is the end... but don't miss our next Underdog Show.
- Sweet Polly Purebred: [singing to the tune of "Oh Where Has My Little Dog Gone"] Oh where, oh where has my Underdog gone. / Oh where, oh where can he be?
- [repeated line]
- Underdog: The secret compartment of my ring I fill, with an Underdog super energy pill.
- [repeated line]
- Savoir Faire: Savoir Faire is everywhere!
- Klondike Kat: [Referring to Savior Faire] I'll boil him in oil! I'll shoot 'im at sunrise! Ooooh! I'll make *mincemeat* outta that *mouse*!
- [opening lyrics for episodes featuring Riff Raff as the villain]
- Chorus: When in this world the headlines read / Of those whose hearts are filled with greed / Who rob and steal from those who need / To right this wrong with blinding speed / Goes Underdog! Underdog! Underdog! Underdog! / Speed of lightning, roar of thunder / Fighting all who rob or plunder / *Underdog!* Underdog! *Underdog!*