From Nookipedia, the Animal Crossing wiki
Tortimer, the mayor, is present at the events, which take place around the Wishing Well. After speaking to Tortimer, the player will receive a medal which can be placed in their home. Each event has its own music, which replaces the hourly music in the surrounding acres. All participating villagers wear white outfits - girls have a pink stripe along the side, while boys have blue stripes.
There are four events in the fair, each lasting for two hours. Here are the events, in the order that they take place -
At 9 a.m., Copper heads an aerobics session that four villagers participate in, mimicking his actions. The player also can participate, using the C Stick to control the motions. Occasionally, villagers will lose their place and start to panic. The event ends at 11 a.m..
The foot race is an event that begins right after the aerobics session, running for two hours. Four villagers will participate, while a fifth villager acts as the starter. There is a race for each gender, each involving running around the Wishing Well five times. The winner and loser of each race will both show emotions after the race is over. The non-participating villagers will be on the sidelines cheering. While racing, villagers will frequently trip over, much to their embarrassment. The player can also participate, using the B button to run.
The ball toss is the third event in the sports fair, starting at 1 p.m. and ending at 3 p.m., two hours later. Two teams of two villagers will repeatedly throw balls into a net, while another villager will cheer on both teams. Many of the villagers are confused by this sport, while others will find it pointless.
The final event in the sports fair is the tug-o-war, which goes for two hours starting at 3 p.m.. Two teams of two pull a long rope across a red line, while a fifth villager waves a red flag enthusiastically at them.