Currently only our mobile players, signed in with Facebook, are able to get this particular outfit as it uses this social feature to award it.
When playing on a mobile device, you need sign in with Facebook (if you haven't already), and invite 7 friends to play. Here are some steps to invite friends:
1. Open Sir Match-a-Lot
2. Tap the Free Gifts! icon on the left-hand side
3. Tap Invite Friends
4. Follow the on-screen instructions to send an invitation to 7 friends total.
After 7 friends have been invited and played the game, that new outfit should appear in your Mailbox.