Season 1 Episode 3. The Brooklyn/Italian Plumber in red battles the lazy, bad skeleton pun making skeleton who will win.
Sans and Frisk were watching their granddaughter from their daughter & son-in-law Frans and Casriel Dreemurr, Klonoa Dreemurr because Frans and Casriel were going to Grillby's for their 15th wedding anniversary to eat some fancy food and make out with each other.
Mario then comes into Frans and Casriel's house and scares Klonoa Dreemurr. Sans becomes incredibly pissed off and fire a gaster blaster at Mario. Mario then jumps out of the way to keep himself in fighting shape.
Sans: You are now gonna have a bad time plumber. *Right eye glows.*
HERE WE GOOOO!!!!
Mario then jumps to try and land on Sans' head, but he misses. Sans then fires 128 gaster blasters at Mario and he lands all of his attacks on Mario with all of the gaster blasters. Mario then uses a fire flower and throws fire balls at Sans, but he dodges Mario's fireballs by teleporting everywhere.
Mario then uses the metal cap to give stronger attacks, however Sans was controlling Mario's soul and bashed him into everything to damage him a lot. Mario then healed himself with a mushroom and got back into fighting shape.
Sans then throws a bunch of bones to try and slow Mario down which worked out for Sans. Mario then decided to freeze sans with the ice flower, however Sans was too fast for Mario to land a hit on him. Mario became warn out and tried using a mushroom again, but before he could heal himself with the mushroom Sans stopped him and said.
Sans: Not this time.
Sans then rips Mario's arm off and then controls his soul again making him too damaged to move. Finally Sans was about to finish it and he said his final words to Mario before he finished him off.
Sans: GET DUNKED ON!!!!!!
Sans then controls Mario's soul and sends him up into the air and Sans' final gaster blaster blasts Mario to smithereens.
Sans: I warned you that you were gonna have a bad time plumber.
Sans then walks over to Frisk and Klonoa and all 3 of them notice that Frans and Casriel have returned from their wedding anniversary date. Sans then decides to tell Frans & Casriel the story about what happened near their house today.