There are few performers as easy to watch as Justin Timberlake and Anna Kendrick. Both are blessed with that most uncommon superpower – they walk on screen and you instantly like them, no strings attached. So any movie that casts them side-by-side deserves your attention. If that movie is a musical, that movie becomes an instant must-see. But now Hollywood have decided to test your devotion by making them the leads in the upcoming Trolls, an animated musical based on those creepy Troll dolls.