Imagine Steve keeping a swear jar in the tower. Every time someone curses, money goes in jar.

A loud noise is heard from Tony's lab and a shout follows, "OW!! $*%#"

Steve pops his head through the doorframe looking at Tony.

"What was that?" He asks looking at Tony as he sucks his injured finger sulkily.

"Nufin," he replies quickly.

"You cursed"

"No I didn't. I said... 'ow. Shoot'," Tony says with an innocent smile.

"No you said... well you know what you said."

"No I don't."

"Jarvis?"

"Yes Captain Rogers?" A British accented voice resounds through the room.

"Did Tony say a curse word?"

"Yes he did. Sorry Mr. Stark. But I cannot lie."

Steve smiles triumphantly and leave the room. He comes back a few minutes later with a jar in his hands.

"Aww c'mon Steve!" Tony says as he throws his hands in the air frustratedly.

"Tony you know the rules," Steve responds giving him a stern look.

"But-"

"No buts Tony," Steve says cutting him off. "This is for the good of everyone. Now, put a dollar in the jar." He says as he gestures to the jar in his hands.

Tony looks at the jar with displeasure, "... I don't wanna..." 

"Tony."

He sighs dramatically rolling his eyes, "Fine!" He grumbles something under his breath, taking out a dollar and stuffing it into the jar.

"There you go Capsicle," he says grouchily.

Steve smiles looking at Tony, "Now, hopefully this serves as a reminder to think twice before you curse."

"Yeah yeah... whatever ya say," Tony responds walking out of the lab. He brushes past Bucky and heads to his room.

Bucky furrows his brows, wondering why Tony seemed to be in such a grouchy mood. He then sees Steve walk into the hall, "Ohh hey Buck."

"Hey Steve. What's up with Stark? He seems... mad about something?"

Steve chuckles as he shifts the weight of the jar in his hands, "Well, let's say he had to contribute to society thanks to his sailors mouth."

"His... Sailors mouth?" Bucky asks clearly confused.

"Yeah. See I have this swear jar. Whenever someone curses, they have to put money inside. Depending how bad the curse word is will determine the amount of money they have to put in."

"Ohh..." Bucky responds with a nod.

"Yeah... So don't let me catch you cursing Buck," Steve says with a pointing a finger at his friend.

Bucky laughs shaking his head, "Okay mister Language Police. But you curse too you know. You've got the worst mouth that I know."

"Yeah but they made their assumptions of me," Steve responds with an expression of pure innocence on his face. "So, their assumptions should be good enough for me to buy myself a new bike don't you think?"

Bucky eyebrows rose in shock as he stared at Steve, "You conniving little trickster."

Steve smiles smugly holding his jar close.