What's the Worst That Could Happen?

Most likely: No one will notice if your shoes aren't the same shade of beige as your purse, but their colors and looks should be complementary, says Stacey Mayesh, a fashion stylist based in New York City. If you're wearing dressy, high-heel pumps, go with a sleek clutch. Casual weekend loafers call for a breezy canvas carryall. Summery sandals look best with a light-colored tote made from straw, canvas, or nylon, while winter boots pair well with a structured leather handbag.

Worst case: If you're a celebrity, you'll wind up on worst-dressed lists. If you're a regular old civilian, you'll just look uncoordinated.

Most likely: According to New York City veterinarian Jennifer Gabriele, eight times out of 10 nothing will happen if you and Muffin share hair products. In fact, some groomers and breeders prefer human shampoo to dog shampoo, using products like Head & Shoulders (to prevent dandruff) and Pantene (for a silkier coat). Just make sure your dog doesn't have sensitive skin.

Worst case: If your dog is allergic to ingredients in the human shampoo, he could develop a rash, swollen skin, or, in very rare instances, breathing problems.

Most likely: If you cook the egg thoroughly (to 160 degrees F), nothing will happen, particularly if it cracked after you got it home and you use it immediately. (This is true even if the egg is infected with salmonella.)

Worst case: A cracked egg is more susceptible to contamination than an uncracked one because the environment inside an egg is more bacteria-friendly than the shell is. A healthy adult who eats a bacteria-infected egg that's not properly cooked will at worst get food poisoning.

Most likely: Your chances of getting ticketed are slim. However, some cities―including St. Paul and Milwaukee―target jaywalkers as a way to raise money, fining each perp as much as $60.

Worst case: A collision. In 2006, more than 1,000 people were killed in the United States while improperly crossing the street. For a jaywalker (jay meant "stupid" or "fool" in early-20th-century American slang), the real mean streets are in Delaware, Florida, and New Mexico, which have the highest number of pedestrian fatalities per 100,000 residents, according to a 2006 study by the National Highway Traffic Safety Administration.

Most likely: Nothing will happen. Your half-finished bottle of mineral water or bag of homemade brownies won't get you booted, and you won't have to fork over a small fortune for concessions. "Nothing really bothers us unless it's smelly, alcoholic, or slippery if left on the floor," says Steve Gaines, a manager for City Cinemas, in New York City.

Worst case: Humiliation. An usher may ask you to eat your food outside the theater. Moviegoers who refuse to give up their snacks could be asked to leave, but their money will be refunded.

Most likely: If you don't have overdraft protection, the vendor and your bank will nail you for charges that typically range from $20 to $75 combined.

Worst case: You may face other penalties: If you're paying off a credit-card bill, you could be charged a late fee, plus interest on the outstanding balance. Depending on state laws, the incident could go on your credit record.

Most likely: Contamination is more likely with ground beef than it is with full cuts. However, getting sick from a burger is still fairly uncommon.

Worst case: For most healthy adults, the worst that's likely to result from eating a rare hamburger is food poisoning. At its most severe, it could land you in bed for several days with a stomach illness. The U.S. Department of Agriculture recommends that you never eat a rare burger (cooked to less than 160 degree F), since bacteria may survive in it. This is particularly important for the very young, the very old, the immunosuppressed, and pregnant women, who are all more susceptible.

Most likely: Gum isn't going to sit in your stomach for seven years―or even seven hours. "Digestive enzymes in the saliva start breaking it down in your mouth and keep doing so all the way down," says Brenner.

Worst case: As with anything else you swallow, you risk choking.

Most likely: Nothing will happen. "You won't get an odor within 8 to 12 hours," says Lucinda Ottusch, lead home economist at the Whirlpool Institute of Fabric Science.

Worst case: If it's very humid, mildew can develop and create an odor or, over a long period, tiny stains in the clothing. Mildew freckles, left untreated, can rot the fabric. To get rid of mildew, soak the clothes in warm or hot water (depending on the care instructions) with a cap-full of detergent.

Most likely: You know you're supposed to change your car's oil every 3,000 miles, but sometimes you just can't get to Jiffy Lube right away. Luckily, even the lube dudes who have a vested interest in this ritual admit that you can get away with changing the oil at 7,000 or 8,000 miles. "This rule is something formulated by the oil-change industry," says Automobile Club of New York manager of public information Robert Sinclair Jr. "It's wasteful."

Worst case: If you wait until 10,000 miles or so, your oil may turn to sludge and your engine might seize. If you willfully ignore the knocking under your hood, you probably deserve to pay the $2,000 (or more) to replace your engine.