This is set towards the end of AoU. My take on what would have happened if Natasha was able to calm the Hulk down.

"Hey Big Guy. Sun's gettin' real low," she said as she timidly reached for him with his hand.

The Hulk's breathing evened out as he lifted his hand.

After Bruce had fully transformed back into himself, he was lying on the ground. He found that the concrete was slightly uncomfortable, especially since he didn't have a shirt on. Once Bruce had stilled, Natasha kneeled down and then straddled his waist. Bruce lifted his head when he felt Natasha on top of him.

"Hey," she said.

"Did you push me out of a building?"

"Well…"

"Okay. Strike that. That question was rhetorical. You pushed me out of a building."

"We needed the Hulk, and-"

Bruce laid back against the concrete. "We were having a cute moment and you pushed me. I can not believe I am falling for someone who pushed me off a building," he said with a smile.

Natasha laughed. "You literally fell for me."

"Wow. That joke was awful. I expected more from you."

"Yeah, well when you spend all of your time with five idiots, they tend to rub off on you."

Bruce laughed at her and then they both went silent.

"We need to leave."

"I know."

"How?" he asked.

Natasha paused for a moment. "Ultron is on a hellacarrier. I bet I know someone who can, I don't know, just jump on up there."

Bruce lifted his head. "No. No no no. That is too high for me to jump up there with you."

"I trust you," she said.

"I don't."

"He's not going to let anything happen to me. He's just as fond of me as you are," Natasha said with a smirk.

Bruce let out a huff. "Okay. You might want to back up a little." He smiled. "It's a little difficult to get angry when you're on top of me."

Natasha laughed and then pecked him on the lips. She stood up and backed away. Bruce began to shake and she watched as his eyes and skin started to turn green.

"Welcome back. Alright Big Guy, you know what to do?"

The Hulk grunted in affirmation.

"Good. Let's go," she said. The Hulk held out his hand so that he could swing her onto his shoulders. Natasha locked her arms around his neck. "Don't let me fall."

"Never," the Hulk responded, to her surprise. The Hulk looked up at the sky, searching for his target when he spotted the hellacarrier. Natasha closed her eyes and held on tighter when she felt the Hulk shift before launching them towards the aircraft.

Natasha was relieved when they finally landed. The jump didn't last long; probably only about 15 seconds, but hurtling through the air on the back of a "screaming green rage monster" was not one of her favorite methods of transportation, even if she was the world's greatest superspy.

"Oh for God's sake!" she heard Ultron yell as he was thrown out of the back of the craft. She couldn't help but laugh at that. The Hulk turned when he heard her laugh.

"Hey Big Guy. You did great. But now I need Bruce," she said.

The Hulk grunted and then nodded. He didn't seem to like the small space anyways. For the second time that day, the Hulk transformed back into Dr. Banner.

"Are you alright?" she asked.

"Yeah, just give me a minute," he said. "One transformation is rough, let alone two. Are you alright?"

"I'm fine. The landing was a little rough but it was nothing I couldn't handle. You did fine," she replied.

She let him sit in the co-pilot seat. Bruce closed his eyes and leaned his head back.

"Any suggestions on where we should go?" he asked.

Natasha allowed herself a half smile. "I have a few ideas."

A/N: I have a few more ideas for one-shots. Prompts and reviews are welcome!