A/N: Standard disclaimers apply. Thanks to DawnFire for beta-ing. Enjoy!
"I still want to be Thor," Geordi said.
Worf looked down at him. "With all due respect, Commander, I doubt you could portray a convincing god of thunder." The Klingon turned Mjolnir over in his hands, apparently pleased with his costume.
"Yeah, I guess," Geordi conceded. "It's just that Data and I had a blast with coordinating costumes last year."
"Well, we're all from the Avengers canon," Riker pointed out. "And I don't think Worf could be a convincing Bruce Banner." He clapped Geordi on the shoulder, and the engineer winced. An Iron Man suit wasn't really gentle.
"He could make a convincing Hulk, though," Geordi mused. "Oh well, that's what the holodeck's for."
"So, w-what are we waiting f-for?" Barclay asked, his Captain America shield quivering with his shaking hands. "N-not that I mind waiting..."
"No, Nick Fury and Black Widow should have been here already," Troi said, tucking a loose strand of hair back into her 1940s wig. At everyone's questioning looks, she said "Captain Picard and Doctor Crusher. Oh, there they are!"
The captain and doctor walked down the hall towards the group. Picard, however, was missing the eye patch and trench coat everyone was expecting. Instead, he wore a vest and quiver of arrows slung across his back.
"Hawkeye?" Riker asked, bemused.
"Well, I met up with Black Widow here and we agreed that the Avengers wouldn't be complete without him," Picard said. He glanced at Beverly, and they shared a mischievous look. "So I did a last minute costume change."
"Yeah, Worf," Geordi joked, then sobered as Worf glared down at him. "Uh, speaking of which, where's Data?"
"He'll be coming along later," Picard said. "Shall we?"
They stepped forward, and the holodeck doors opened.
The cosplayers were immediately surrounded by people congratulating them on their costumes. They reacted suspiciously in character - Barclay and Geordi being uncomfortable with the attention, Picard and Crusher being polite and friendly, and Riker reveling in the attention and his new flying abilities. Only Worf was out of character, acknowledging everyone's comments with a surly nod.
Geordi was demonstrating the Hulk projection he'd programmed when, all of a sudden, the lights went out. The festive music came to a screeching halt, and silence fell over the room as everyone wondered what would happen.
"Mortals, look how far you've fallen."
A loud *clang* rang through the holodeck as Barclay dropped his shield in terror.
"Dressing as creatures of which you can only aspire to be a pale imitation." A spotlight flashed on, illuminating a single figure. "Capable of creating whatever you desire, you create this meager palace of Midgard!"
The haunted castle setting was hardly meager, but in comparison to the speaker - slim, pale, clad in black and green and gold, eyes a bright, strange blue - it paled.
"I am Loki, of Asgard," Data proclaimed, spreading his arms. "And I am burdened with glorious purpose."
Troi timidly stepped forward, and he whirled to face her, his coat and cape whipping behind him. "Stand back, you mewling quim!" He brandished his staff, and Troi retreated, leading everyone else in taking a step back.
"The bright lure of freedom diminishes as you congregate in this space, this chamber you call the 'holodeck'."
A few titters escaped the crowd, and Data's eyes narrowed. "You think I jest, mortals? Kneel!" He raised his staff, and a bolt of energy arched over the crowd.
Everyone dropped to their knees to avoid the blast, and Data laughed. "Where are your Avengers now?"
"We are here!" Picard yelled, and loosed an arrow. Guided by the holodeck's systems, it flew straight towards Data.
Who caught it, and laughed again.
The Avengers leapt into action. Beverly did a backflip, Picard nocked another arrow, Worf yelled and swung Mjolnir, Geordi activated the Hulk projection, and Riker fired off a blast from his hand.
Data dodged the blast and sent off another bolt. Barclay raised his shield to deflect it, and Picard ducked, letting go of the bowstring.
The arrow glanced off of Geordi's back as he lifted Data and slammed him to the ground (counting on the safeties being on). Data dematerialized as he hit the floor, and Geordi deactivated the Hulk.
The room exploded into cheers, and they took a bow. Data reappeared a few seconds later, his hair and clothes mussed and missing his staff, and bowed.
"You don't look too bad for someone who just got Hulk smashed," Geordi said once the crowd thinned.
Data lifted an eyebrow. "Gods cannot be destroyed so easily," he said matter-of-factly.
Geordi laughed. "You did great."
"As did you. Does that mean I participated appropriately in the celebration of this holiday?"
Geordi nodded vigorously. "You went above and beyond. In fact, I think this has been the best Halloween I've ever had."
Data looked pleased. "I hope it continues to be according to the traditional greeting, Geordi."
"Happy Halloween to you too, Data."