First challenge... is virginity. Roy Mustang and his crew share stories about losing their virginity, Hikaru's first time, or Duo mocks Heero for still being a virgin at 15 - when we say virginity, we mean it literally this time.
Have fun! And have 80 minutes to complete it.
Challenge Two: Threesomes
This challenge is on threesomes. It doesn't have to be sexual - it can be fraternal as well.
Explore a three-way relationship and the dynamics of "three's a crowd"... but it also provides balance. Think of the genin teams of Naruto, the Seigaku Power Triangle (Ryoma, Fuji, Tezuka), or the three Talisman Senshi (Uranus, Neptune, Pluto).
Basically, use three characters who have some time of bond.
You have three-half hours, a.k.a. 90 minutes.