If you see a particularlygood looking person, with pecks and abs and six pack etcetc. then you can call them 'sex on legs'. They give joy to your eyes, and, in this way link to sex. Just not in bed, but on legs.
This is a controversial day when if you look like actual sex on legs you have the right to be able to do anything you want without taking blame nor punishment. This important day occurs on the 28th of February
Beth: *Eats a sock and a dinosaur*
Taya: What is wrong with you dude
Me: It’s sex on legs day she can do whatever she wants.