It comes from a David Mamet play, and there's two con artists in the play, and the woman is conning the man, and the man looks at the woman and says, "Oh, you're a bad pony, I'm not going to bet on you."
Dolazi iz predstave Davida Mameta. Tamo su dva glumca varalice, žena prevari muškarca, a muškarac pogleda ženu i kaže “Ti si jedan zločesti poni, neću se kladiti na tebe.”