Put a playful spin on a formal dinner and ask guests to dress in costume from one of the most popular decades in modern history -- the roaring '20s. Encourage female friends to dress as flappers in short, beaded dresses and long strands of pearls, and ask male guests to don top hats and tail coats. Use this theme for a formal sit-down dinner, costume party or New Year's Eve blow out, and don't forget to mix plenty of Prohibition-style cocktails like sidecars and highballs. You can even adopt this theme for a wedding by dressing bridesmaids and groomsmen in the fashions of the time and let your wedding guests in on the costume fun, too! Hire a jazz band to play during the reception, and -- if you can afford it -- reserve a corner of the venue for a cigar bar.