The Guy-Who-Doesn't-Partake-in-Casual-Fridays Guy
You know this guy: He just doesn't do casual Fridays. He totally blows it off. This has more risk than you think.
What it says about you: It can go one of two ways. On one hand, you can be seen as the hardest working guy. The guy that doesn't even realize it's Friday because he is too focused at work. This is hard to pull off, but if you can, your bosses will love you. They will think you are so dedicated that you forgot it's Friday and you are on your way to becoming a managing director. However, if you are the only one that isn't casual on a Friday, you might look like you are too cool for school and alienate your co-workers. You are their version of Barry Bonds. Or even worse — they might think you're interviewing somewhere else and that will make nobody like you.
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The Too-Casual Guy
Even though it's Casual Friday, there is still a dress code. If you are ever in doubt as to whether something is too casual, the answer is YES. Don't be a moron and push the limit here by wearing flip-flops or a Hawaiian shirt, or failing to do basic grooming like brushing your teeth or combing your hair.
What it says about you: If you can't even manage your own hygiene, you are not to be trusted with any account — even the lunch account.
Not only could you ruin your career, you could lead to your company outlawing Casual Fridays altogether, which is cause for banishment to Siberia.
Every company has a dress-code policy, so read it — even for the humor of it. My favorite was reading the unacceptable attire list. At one place I worked on Wall Street, the no-no list included: T-shirts with logos, blue denim jeans, deck shoes, evening wear, thongs of any kind, underwear as outerwear, tank tops, and provocative or revealing attire.
Really? There are people who require clarification on these items?