Evolutionary biology has all sorts of goofy-sounding titles (the sexy son hypothesis! The gay uncle hypothesis!) but my favorite is the "rock paper scissors" mating mechanism of the common side-blotched lizard.
The lizards, which roam the deserts in Nothern Mexico and the American West, come in three colors which correspond to behavior:
Orange-throated: bigger, have large territories, pursue many females
Blue-throated: smaller, have small territories, pursue one female
Yellow-throated: dubbed the "sneakers," they resemble females and can sneak into the territories of other males, swooping in and "stealing" unattended female lizards
As described in the original 1996 study published in Nature, the lizards form their own unwinnable game of rock paper scissors: the ultradominant orange lizards will beat the monogamous blues, but because the orange-throated lizards have such a huge territory, the sneaky yellows can swoop in as Mr. Steal Your Girl. Blue-throated lizards, who are vigilant and known to help fellow blues, don't let wily yellow-throated lizards get very far. Essentially, orange beats blue; blue beats yellow; yellow beats orange.
Check out footage of the lizards in this video by PBS Digital Studios.