These are just ideas, deviations on actual events. I wrote my first one for the Writer's Guild http://www.comicvine.com/forums/fan-fic-8/the-writers-guild-presents-9-13-13-1496777/#8 where Hawkeye had the symbiote instead of Spider-Man, merely because he went into the room before hand.
This runs on the premise of the below picture, which I have edited the second panel.
What If Henry McCoy gave the 'beast' formula to someone else?
Henry held the newly created formula in his hand. Part of him wanted to drink it there and then, to boldly go where other scientists like Salk and Hoffman before him. But soon his logical rational brain kicked in.
"I need to test this, observe the results, test my hypothesis" he said to the formula "If it is indeed a toxic substance then I have the antidote, but testing it upon myself...Bobby!"
Henry packed up his equipment and rushed from Brand Corporation towards Westchester.
"So you want to test your jungle juice on me?" Bobby Drake slid around the Danger Room on an ice slide.
"I need a mutant with an obvious mutation" said Henry.
"What about Warren?"
"Are you...chicken?" baited Henry.
"Hey big foot!" cried Ice Man as he slid in beside his friend "Not cool calling me a chicken! Besides I think you're chicken for not asking Cyclops!"
"Are you going to help me or not?" huffed Henry "This could help humanity, not just mutants"
"You better thank me so many times when they give you the Nobel Prize!" Bobby reverted to human form "Is it an injection? I hate needles"
Henry smiled and handed a test tube to his young friend "It's injested"
"Smells like your sock drawer Hank!"
Henry smiled "One small drink for Bobby, one giant leap for everyone"
Booby held his nose and gulped down the formula.
"What the hell is that thing!" yelled Cyclops as he fired his optic blast to parry the shard of razor sharp ice pelting down on them.
"IT'S BOBBY!" yelled Hank leaping to safety.
"I'm trying to contact him via telepathy but the ice is, well blocking it" said Jean as she tried to wrestle him mentally.
"BOBBY! I'M SORRY!" called Hank as the massive Ice-Beast ran rampant across Xavier's School For Gifted Youngsters. A massive glacier fist smashed a hole in the floor.
"What happened?" snapped Cyclops.
"He drank my formula. I needed a test subject to see what would happen if you mutated a mutant" said Henry.
'What?" Cyclops fired some more blasts.
"Is there an antidote or something?" cried Warren as he buzzed around his friends head like an annoying fly.
"I hav..." Henry's sentence was ended as a blast of ice sent him flying through a wall in an avalanche of ice and snow.
"HANK!" Jean screamed as she tried to coat him in a tk shield as the other two X-men took on the ice giant.
"So I'm stuck like this?" Bobby looked at his new jagged form. Henry McCoy didn't know where to look as he could feel all the eyes of the X-Men boring into him like daggers