Steve woke up feeling extremely dehydrated and hungry. True, he often woke up hungry, due to his metabolism, but this was a different hunger. This felt like he hadn't eaten in days, which was obviously wrong. His neck was also stiff, as if he hadn't slept on his pillow. Opening his eyes, Steve discovered why his neck felt the way it did: he had fallen asleep in Tony's lab.
How did that happen? He blinked his eyes, before looking disbelievingly around the lab, which was a large mess. Granted, he always thought that the lab was a mess, but it seemed even more out of sorts than usual. The table which seemed to have served as his bed last night was covered with mechanical parts, which looked like they belonged to some part of the Iron Man armour. Steve shook his head in fond exasperation Does his mind ever rest?), before looking around for the inventor. Steve could not see him anywhere, which was odd. He normally wasn't allowed in the lab without Tony.
Steve shook his head, I'm sure that he's around somewhere, looking for something or other, before deciding to stand up and stretch his tight body.
Once Steve had begun to stretch, he had quickly discovered that he was unable to touch his toes, which was normally a simple stretch for him. Frowning, he began to stretch his arms across his body, before feeling a tight pull in his chest.
Now what could be causing that? Steve placed a hand on his chest, in an attempt to feel his heart beat for any irregularities. Instead of flesh, he felt... Metal? Steve lifted up the shirt, pulling it off of his body.
This looks like the arc reactor, Steve thought, tapping the metallic case on his chest, but why would I have one in my chest? Unless... Unable to touch my toes? Waking up in Tonys lab? No, it can't be, but that makes the most sense. I am in Tony's body.
"Uh, JARVIS?" Steve asked tentatively, thinking that his voice sounded distinctly like a certain billionaires.
"Yes sir?"
Steve let out a sigh. JARVIS only calls Stark sir.
"I'm not dreaming, am I?"
"Vitals indicate that you are indeed awake, sir."
"Yeah, I thought so," Steve muttered, sitting back down and putting his head in his hands.
"Sir, Agent Romanoff has called for a team meeting."
"Now?"
"Indeed, sir."
"I am on my way."
Steve got up, shaking his head. It seems as though it's going to be one of those stranger days.

Thor lay in his bed, sleeping. He had returned to the tower early in the morning, having spent the evening with Jane in New Mexico. Snoring, he was awoken by the sound of a waterfall. Frowning, he opened his eyes.
"This is not my room," the Prince muttered, looking around. He saw a very organised room, much more than his had ever been (in either Asgard or Midgard.) The sound of the waterfall was also very calming, if he was honest, but was also out of place. Perhaps I was even more sleep addled than I remember, and did not fall asleep in my room?
"JARVIS, please remove the waterfall from the room."
"Of course, Doctor Banner."
Thor looked up at the roof in confusion.
"JARVIS, are you malfunctioning? For you just referred to me as Doctor Banner."
"I am operating at peak efficiency, Doctor Banner."
Thor scowled. "Do not mock me, machine. I am Prince Thor, of Asgard."
"Then perhaps I am malfunctioning, for vitals and voice recognition indicate that the current occupant of the room is Doctor Banner."
Thor could feel his anger growing. As the anger grew, his mind began to feel clouded, as if some external force was fighting to gain control of his body.
"See for yourself, machine," Thor got out of the bed, walking to a mirror. "Behold-" he looked in the mirror, and he felt all his anger fall away (as well as the foreign force in his head), only to be replaced by confusion. "-Doctor Banner?"
"Indeed, it appears that I am not malfunctioning."
"Verily," Thor muttered, touching his face, and looking at Doctor Banners reflection.
"Agent Romanoff has called for a team meeting."
"I will... I will be there presently," Thor said, unsure about who he truly was.

The first three chapters will be a bit repetitive, since its each of the Avengers discovering that they are no longer in their own bodies. After that though, things should get a bit more interesting.
So, that's four down, two to go- I feel that the swaps that I have chosen are somewhat obvious, but they just seemed so right (and they wouldn't let me change them. Characters can be stubborn sometimes.)
There is a vague outline of where this story is heading. Vague= I know some interesting scenes that I want to write, but can't until I set it all up.
Anyways, thanks for reading, and any comments are highly appreciated.