4x100m Relay (Mario & Sonic at the London 2012 Olympic Games for Nintendo 3DS)

4x100m Relay is an Athletics Event that appears in the Nintendo 3DS version of Mario & Sonic at the London 2012 Olympic Games. The aim of the event is for the last of the four runners in the team to cross the finish line first, with the game version placing a significant focus on the passing of the baton between runners. The starting world record for this event is 0:37.04, with the starting Olympic record being 0:37.10. The character set for this event is Heroes, meaning that Mario, Sonic, Luigi, and Tails are playable.

Gameplay
In this event, the team of the four Heroes competes against three teams of blue, yellow and green Shy Guys. After showing the start of the relay, the event starts at the first baton handover, where the player must first slide left and right on the touch screen to cause their character to run further and increase the amount of time for the baton to be handed over. A meter will then be shown with the receiver's hand on one end and the current runner's hand and baton on the other, which will move to the receiver's hand over time. When the baton reaches the receiver's hand, the player must touch the touch screen to pass the baton. Their timing will affect the speed of the character after the baton pass, with a Perfect rating giving the greatest speed boost, followed by Great, Good and Bad giving no boost. The meter will slide forwards twice and backwards once before giving a miss and decreasing the character's speed. This is repeated for the other two baton passes, before reaching the final sprint, in which the player needs to quickly slide forwards and backwards to increase their character's speed and reach the finish line.

In multiplayer, all players play co-op in a single team. Unlike single player, the players can choose their characters; in a 4-player team, the relay order is P1 > P2 > P3 > P4. With 3 players, P1 takes control of the first and fourth characters; with 2 players, each player controls two characters each. The player receiving the baton must slide left and right, while the player passing the baton must touch on the touch screen with perfect timing. In the final sprint, it will say "Everyone slide!"; all the players must slide left and right to make the final character charge power to do a special dash.

Controls
1) Running start: Slide ⇔ on the Touch Screen. 2) Baton pass: Touch the Touch Screen.

Medley Match
In Medley Match Mode, 4x100m Relay appears as the third event in 4P Co-op Medley 1 and 4P Bonding Medley 2.

Story Mode
4x100m Relay appears in the story mode as the challenge of Heroes Episode 2, The Secret of the Fog, in which Mario, Luigi, Sonic, and Tails must beat a team of three blue Shy Guys and Eggman Nega.