Disclaimer: I own nothing! Nothing! It's-a me!
Xander snorted in frustration. The little brat ahead of him grabbed the last gun out of the bin and now he didn't have enough for most anything else. Eventually, he purchased a pair of white gloves and a red cap from the 'bits and pieces' bin out of a need for something to buy.
It was only when he got home and saw a pair of blue overalls in his closet that he got the idea for his final costume. A little bit of effort, a red shirt, a large store-bought mushroom, and orange tulip later; Xander was ready to go trick or treating - well, after he met up with Buffy and Willow.
When Ethan's spell hit, Mario looked around this new dark world he found himself in. Oh well, guess it was time to find the princess once again. How fortunate for him that he was holding a one-up mushroom and a fire flower. Eating them quickly, Mario's overalls changed from blue to red, and his shirt and hat from red to white.
With the help of the kind spirit, Willow, and wise mentor, Giles; Mario had no trouble finding and keeping Princess Buffy (who was far more girlie than he was used to from a princess. She actually made Princess Peach look like that tomboy, Princess Daisy!) out of trouble.
And he taught many vampires along the way why it was not a good idea to upset someone that can toss out endless bouncing fireballs.
The next day, Giles was checking to see if anything remained from the teenagers' Halloween possessions. Buffy could speak and read French. Willow didn't seem to have any noticeable effects.
Xander spoke up. "Well, I kinda want to speak with an Italian accent. I can also throw fireballs still. Oh, and I can do this."
Without further ado, Xander leaped up in a jump most professional NBA players would envy and landed on top of a bookcase. Then he leaped down - seemingly traveling far faster than was normal, and impacted the floor with with enough force to crack the tile. "I can also probably punch up through the ceiling if I wanted to. From the ground."
"Wow, Xander!" Willow exclaimed and started babbling. "The ceiling is two stories up in the library. You still have the red shirt, but no overalls. Can you still do anything Mario was able to do?"
"I'm not sure. But I do know just about everything about plumbing now."
"Great, if ever there's a toilet stuffed up, you can make with your new skills." Buffy was still upset because of her lack of gained powers and her time as princess useless.
"Maybe you shouldn't help Buffy patrol until we find the full extent of your powers?" Giles said.
"Actually, I was thinking the opposite." Xander crossed his arms in frustration. "How better to find the limits of these new powers if I can't use them?"
And so that evening, Xander and Buffy were walking around a cemetery, both still upset. Buffy at sharing her slayer duties and her lack of anything to show for Halloween; and Xander for being treated like nothing. He finally got some useful powers and Giles wanted him to sit on it. No way was he going to - oh hey. Vampires on approach.
"Ahh, a lovely couple on a midnight stroll. How... tasty." said the tall vamp wearing a dark leather biker's jacket. By the looks of him and the way he moved, he wouldn't have been a linebacker or anything, but he did seem to know his way around a brawl.
"Oh yeah. A midnight stroll through a cemetery." Buffy quipped and pulled out a stake. "How stupid are you?"
"Not stupid enough not to bring along a few friends." The vampire smirked as twelve other vamps walked out from behind a large mausoleum. Then, one of the new vamps caught fire and burned into dust.
"No. You're still pretty much one with the stupid." Xander smirked while holding up a fireball.
The battle was on. Two against twelve would have been dire odds just one day ago, but with Xander's fireballs cremating vamps one by one, things were much more even. But even so, the teen-aged boy couldn't avoid all the punches. One got through.
The effects were immediate. Xander's red shirt turned blue, and when he tried to toss another fireball, nothing happened. There were only four vamps left, but one of them was the leader. And before Buffy could do anything, the leader of the vamps lashed out and punched a stunned Xander once again.
When Xander stood up despite the pain, he noticed his clothes were a little too big for him. He had lost some height, maybe half a foot. Mentally, he thanked whatever powers that be that he didn't turn into a mini-Xander. 5'4" he could handle. Three-foot-nothing would have been utterly humiliating.
It was then he noticed the head vampire was behind him and closing in. "I'm getting tired of this." the vamp said.
Buffy screamed, "Xander!"
He felt two hands on either side of his head. Then there was a large crack as Xander's neck broke.
Buffy was about to cry out once again, when Xander's body suddenly vanished - surprising her and all the remaining vamps.
Without knowing any better, the Slayer threw herself into the fight to avenge her friend.
There were only three vamps left when Xander arrived. "Hey guys, did ya miss me?"
"Xander? How?" Buffy backed off from her opponents.
"Guess I had an extra life. Tomorrow, I'm going to eat soo many mushrooms." Xander smiled. He regained his normal height when he stopped by his house and ate the second mushroom he had purchased from the store - as the large ones came in a shrink-wrapped two-pack. He wondered if there was a 99 extra lives limit or a 999 one for him. "I found myself back at the school of all places. But hey, guess what I picked up along the way?"
With that, Xander lifted up a massive sledgehammer as thought it weighed nothing. He figured that compared to those giant flaming wooden barrels Donkey Kong threw at his Halloween alter ego, smashing through vampires would be easy.
He was right.AN: Most probably a oneshot - but I had the idea of what would happen if the costume was from the Mario series and things worked like they did in the game.