Track and field athletes don't have to wear shoes. While shoes are almost always wore by athletes competing in track and field events, they're not required. But there are rules about the shoes. Adam Pretty - Getty Images
Gymnasts can't wear colorful nail polish. While gymnasts can wear colorful makeup, bright nail polish is a no-go. It's either neutral or none at all for these athletes. Ezra Shaw - Getty Images
Olympic athletes are not allowed any form of protest while competing. Athletes are not allowed to express any form of protest on the field of play, in the Village, during ceremonies, or at the opening and closing ceremonies. The rule was put into place prior to the 2020 competition and has faced significant pushback. Bettmann - Getty Images
Athletes can have endorsements. They just can't talk about them. When it comes to endorsements , athletes can have them and get paid for them. However, during the games, the athlete can't mention them, and the company can't promote the athlete either. Bruce Bennett - Getty Images
Pants are a must for men's skating. While you may think male figure skaters could wear tight a la dancers, that's not the case. Trousers are a dress code requirement. ARIS MESSINIS - Getty Images
Women's figure skating competitors must wear skirts. While men have to wear pants, ladies aren't allowed. Even if they're simple and sheer, a skirt is required . MLADEN ANTONOV - Getty Images
Some athletes can't drink. Per the International Olympic Committee, drinking is allowed . Athletes can even bring in their own alcohol to the Village. However, some athletes have no drinking rules imposed by their country. For the USA's athletes there's no booze in the Village but outside, it's fair game. MARK RALSTON - Getty Images
Athletes can't post photos of the field or backstage to social media. While athletes can use and post to social media during the games, there are restrictions. Images and video showing the field of play or backstage areas like athlete and coach only ares are off limits. MARTIN BUREAU - Getty Images
BMX riders must tuck in their shirts. BMX athletes are required to tuck in their shirts even if it is to matching pants. Phil Walter - Getty Images
No backflips allowed in figure skating. While cool, back flips aren't allowed in figure skating because of the two-foot landing that discounts it as a "jump." That didn't stop 1998 competitor Surya Bonaly from nailing one for fans, though. ERIC FEFERBERG - Getty Images
Those who swing second in hockey fights get less penalty time. While fights are rare in Olympic hockey , athletes don't want to start one, but they may want to finish it. While instigators get five minutes in the penalty box, those who drop the gloves second only get two. BRENDAN SMIALOWSKI - Getty Images
Basketball players can dunk but can't hang on to the hoop. Dunking is allowed in Olympic basketball . However, players aren't allowed to hang onto the hoop after doing so. Jed Jacobsohn - Getty Images
Swimming world records must be faxed in by athletes. If a swimmer sets a world record , it's not automatically recorded. Athletes have to fax in their record. Yes, fax. Al Bello - Getty Images
Fencers can't leave the field of play or they forfeit. This may not seem odd, but it is. If a challenge or appeal is wanted during a match, the athlete cannot leave the piste or field or play. In 2012 South Korea challenged a call, and fencer Shin A-lam was forced to stay on the piste for nearly an hour before a decision was made. Tom Pennington - Getty Images
Wrestlers must carry a handkerchief. Olympic wrestlers have to cary a hanky somewhere in their uniform called a "bloodrag." Yes, it is used to clean up any bleeding from competition. Laurence Griffiths - Getty Images
Olympic swimmers can grease themselves but not too much. To avoid chafing, swimmers can grease their elbows and inner thighs, but they can't use too much. Tom Pennington - Getty Images
Water polo players have their toenails checked before competition. Water polo athletes have to clip their toenails in order to avoid some nasty scratches under water. Jeff Gross - Getty Images
No smoking in the Olympic Village. There's no smoking throughout most of the Olympic Village, but there are designated areas for those who choose to do so. FRANCOIS-XAVIER MARIT - Getty Images
Only one piece of handheld food can be taken from the Olympic Village food court. An apple? Yes. An apple and a to-go tray? Not so much. Only one hand-held item or one beverage can be removed from the Olympic Village food court. MARK RALSTON - Getty Images
Beach volleyball bikinis must be a certain size. While there are no options beyond the bikini, if beach volleyball players choose to wear one, the sides of the bottom can't be any wider than 7 centimeters. Stephen Munday - Getty Images
No scoop or v-neck leotards for gymnasts. Gymnasts' uniforms are strictly regulated, and scoop or v-necks that extend beyond the mid-sternum aren't allowed. Alex Livesey - Getty Images
No groin grabbing allowed. Water polo is a tough sport, but there's no excessive force and that includes groin grabbing. Jeff Gross - Getty Images
Lost props stay lost in rhythmic gymnastics. Throw that hoop or ribbon too high in rhythmic gymnastics , and that's too bad. Props can't be retrieved during a routine, and athletes must keep going without them even if their hoop is in a rafter. Laurence Griffiths - Getty Images
A coin toss determines the color of beach volleyball uniforms. If teams show up in the same color, a coin toss gets to decide who has to change. THOMAS COEX - Getty Images
Olympic gymnasts have to pay for a scoring challenge. If a team believes a score is unfair, gymnasts have to pay $300 to have it re-evaluated. If the challenge overturns scoring, the team gets their money back. If it's not, the cash goes to charity. Clive Brunskill - Getty Images
Cyclists' socks can only go to mid-calf. When it comes to Olympic cycling , there's also a strange uniform rule. Socks can't be higher than mid-calf, and they are measured. Bryn Lennon - Getty Images
No hand-holding finishes. Olympic runners who choose to hold hands at the finish line are disqualified due to a rule that says you can't have a contrived tie. Sean Garnsworthy - Getty Images
No excess nudity for figure skaters. Figure skaters don't have a set uniform, but there are major rules. One of them is that there can be no excessive nudity. That's exactly why you see so flesh-toned panels to give the illusion of skin without breaking rules. ARIS MESSINIS - Getty Images
Golfers must sign their score cards. If an Olympic golfer doesn't sign their score card, they are disqualified even if they won. Scott Halleran - Getty Images