From the Super Mario Wiki, the Mario encyclopedia
Waluigi's Ambition (also referred to as Tricksters Episode 1 and Tricksters 1) is the first Tricksters episode in the Story Mode of the Nintendo 3DS version of Mario & Sonic at the London 2012 Olympic Games. This episode is unlocked after completing The Secret of the Fog, and unlocks Stop Dr. Eggman! once it and Wario's Scheme are completed. This episode, along with the other Tricksters and Wild Ones episodes, must be completed to earn the Story Mode 3 badge, and its completion is also required to unlock the Story Mode Cleared badge.
Waluigi is testing out a pair of binoculars that he has made, calling them "Waluigiscopes", and plans to use them to find Luigi's weaknesses. A pair of red and yellow Shy Guys arrive and ask Waluigi if they can borrow the binoculars. Waluigi refuses and shouts at them to go away, scaring the Shy Guys off. Waluigi continues to test out his binoculars, until Metal Sonic arrives and knocks them out of his hands, breaking them. Waluigi gets angry with Metal Sonic and demands that he pays for the replacement binoculars, and Metal Sonic challenges him to an Olympic Event. Luigi and Charmy arrive and witness Waluigi and Metal Sonic challenging each other.
Waluigi defeats Metal Sonic, causing him to run off. Waluigi chases after in pursuit of his money, and Luigi and Charmy follow after them.