Int. Casino
Two men are by a walled betting table. A croupier waits to take bets.
Man: Everything on red.
Man 2: Everything on black
The men hand over their chips to the croupier. A woman walks over to man 2.
Woman: What are you betting on now?
Man 2: Ant racing.
ENDS
The reason I think this doesn't work is that people do actually bet on insect races.
Also, as soon as the woman says: What are you betting on now? it's obvious what the punch will be, or at least some variation on a theme.
I would probably bet on ant racing - I've bet £10 on how many adverts they'll be in an interval before now, so why not?!
Not bad, but it's a bit underplayed.
Maybe she say's bad odd, I have £50 on shoe.