Named after the famously twitchy noses of rabbits, they're not as cute as they sound - especially since they're a dead giveaway to celebrities who've been Botoxed.
Bunny lines are horizontal wrinkles that form across the ridge of the nose - they become more apparent when people smile. As we age, bunny lines will form naturally from years of making facial expressions.
However, when the rest of the face is Botoxed, bunny lines are often the only place the face can move freely, and as a result they become deeper.
As such, cosmetic surgeons, (and now us!) can use this knowledge to spot celebrities who've gotten the face-freezing injections.
Which will be hours of fun the next time you're thumbing through a celebrity weekly.