Who: Nine, Rose and Jack.
When: Probably before Boom Town? Ish. It's not exactly canon.
What: A game of truth or dare reveals some interesting things and ends in a trip to the planet Belgium to find the best chocolate in the universe.
Rating: PG-13 for innuendo. Unless you're Gallifreyan, in which case this probably classes as NC-17.
(
It's generally polite to ask a girl before you... handsex her. )