Puck aka Robin Goodfellow; Costume & a bit of Character immersion?

Okay so it's not exactly a play I'll be in, but I will be uming the role of Puck in something called the Fairy Fest. Essentially I'll just run around all day as Puck, playing tricks on people and causing mischief. I need an easy DIY costume that looks as good as possible, and any tips you could offer. Thanks :)