Adult Group Halloween Costumes Many costumes are designed to be perfect for the whole family. But when it’s time to leave the kids behind or enjoy a late night out on the town, group costumes take a whole new twist. These are the group looks that let you channel some of that freedom you've been earning all your life. Group Costumes. Costume theme's come in a wide range, from humorous and raunchy to sweet and innocent. Many themes that are always popular year after year are actually inanimate objects; these would be the infamous beer themes, cocktail themes, board game themes and even fast food themes.