“Dancing the cha-cha-cha… Oliver Queen and his partner Felicity Smoak.”
[Or the one where Oliver is a celebrity contestant on some alternate universe version of Dancing With The Stars, and Felicity's his professional dance partner. There's sparkly outfits, some fake kissing, some actual kissing, some bam chicka wow wow-ing, and a 98.9% chance they fall in love over the course of 12 weeks. Also dancing.]
They've been best friends since college. And then one night she calls him devastated and he tries to comfort her but they end up in a very non platonic situation. Except she's engaged to be married in a few months and he's not her fiancé. Where does that leave them?