Spirit week can be a chance to have some fun and let the staff dress in weird costumes -- but you can also use it to encourage some friendly competition in the workplace. Letting loose at work is not just fun; it can also be a good thing for the operation of the business. In a study published by Penn State University, researchers found that fun in the workplace increases employee retention and can increase sales -- especially among older workers. On the other hand, manager-supported fun can also decrease productivity -- so the challenge in planning "spirit week" activities lies in planning activities that are fun, but that also encourage efficiency.

Sales Contests

Encourage employees to compete against one another in a fun way by holding a productivity contest. For sales employees, that could simply involve counting the number of sales they make, and publishing the results on a bulletin board in the break room. For customer service employees, you could count the number of calls they make. If you have employees with many different types of jobs, you might also award points for doing other positive acts you want to encourage in the office, such as a "tidiest desk" contest, for example. Naturally, there should be a prize involved -- and one that employees will actually want to win.

Food Competitions

Having a potluck of any kind can encourage employees to stay on the job longer, since they won't have to leave the office to get lunch. To make it even more fun and encourage some fun competition, make it a theme lunch and have everyone vote on their favorites. Hold a casserole competition or chili cook-off, for example, and like always, award someone a prize for winning.

Tie and Scarf Swap

Most people have an ugly tie or scarf in their closets that they never wear. Instead of letting it languish there, organize an ugly tie and scarf day at work. Everyone wears the ugliest tie or scarf they have to work that day, and co-workers can request that you give them your tie or scarf in exchange for theirs. It's a good excuse for people to get rid of ties or scarves they never wear -- and even for women to get rid of ties they wish their husbands didn't have, suggests Paul McGhee, PhD of the Laughter Remedy website.

T-Shirt Design Contest

Have each department in your office design a T-shirt that demonstrates what that department does, the way the department employees see their department, or what they wished they did. Get each department's T-shirt printed for them, and have everyone wear them on the same day. This can encourage your employees to get creative, and can give you good insight into how people view their department or their organization, suggests business speaker Barbara Glanz.