Sonic vs Mario is the episode 21 of the Smash Bros episodes.
Mario is attracted the attention of the blue speedy hedgehog Sonic, who challenges him to fight. Luigi offers to fight in Mario's place. Without wasting time, he attacks, but is easily knocked out by Sonic. Sonic says he is the world's fastest hedgehog in the world. Now Interested, Mario accepts his challenge. Mario charges, but is met by Sonic's Turbo Hurricane and gets knocked backwards. He gets back up and Peach is watching Mario having a challenge as he again charges Sonic, but again, Sonic is able to hit him. Sonic explains that Mario's body can't move fast because Sonic's body moves fast. Sonic continues, making Mario run towards him. Mario goes for a punch, that misses Sonic. Sonic makes a hard blow into Mario's chin, causing him to fly throughout the air. Sonic makes a supersonic technique to finish off Mario, Shadow stops his technique. Mario is about to fall as Tails catches him and Luigi wakes up. Shadow repriminds Sonic that he's the one he is a fake. Shadow and Tails leave before Sonic calls Mario that he is a mustached punk. Sonic rushes off. Mario helps Luigi to get up. The two plumbers leave together.