Natasha

Natasha was coming back from her morning run. She was in the elevator going to the common floor. As the elevator door opened she saw Clint. She walked out of the elevator and Clint suddenly blocked her path.
She looked at him questioningly when he leaned in and kissed her. Natasha was surprised but kissed back.
Clint pulled back and grinned. He pointed upwards.
Natasha saw the mistletoe. She just shook her head and smiled.
Her partner was a child.

Bruce

Bruce was in the kitchen making breakfast. It was his turn. He was making pancakes and waffles that most of his friends like. He turned to get some coffee and found himself face to face with Clint.
The archer had a determined look. He leaned in and kissed Bruce. Bruce was surprised.
Clint broke the kiss, hugged Bruce and said, "Merry Christmas, Big Guy."
Bruce shook his head and said, "Merry Christmas, Clint."

Steve

Steve was coming out of the shower when he saw Clint. The archer had a mischievous glint in his eyes.
Steve shivered. Clint looked very adorable.
Suddenly with lightning fast speed he was near Steve.
Before Steve could say anything, Clint leaned up and kissed him.
Clint then broke the kiss and whispered in Steve's ear, "This is allowed in this century, Cap."
Then he was gone.
Steve wondered how Clint knew.

Tony

Tony was in the lab working. Pepper had just broken up with him last week saying she couldn't handle him anymore.
There was a tap on his shoulder.
Tony turned around and found a pair of lips on his own.
Clint was kissing him. Tony kissed back.
Clint pulled away and said, "Cheer up its Christmas."

Thor

Thor got a lap full of Clint who then kissed him.
Thor kissed back enjoying the feel of those supple and full lips on his.
Clint then said, "Midgardians do this during Christmas to show their love."

The Avengers were all kissed by their adorable Hawk.