Tony was known for laughing at people's mistakes, their looks, their stupidity, anything really. This time, though, it wasn't really a person he was laughing at and they weren't being stupid. It was Jarvis, and he was whistling.
In a weird, twisted way, it kind of made sense for Jarvis to be whistling, considering yesterday's events and as Tony looked back on it, he began to laugh harder. Tony had been sort of happy, for lack of a better word, yesterday while he was working on a project and had begun to whistle unknowingly.
Jarvis had asked why he was whistling, because for as long as he had worked for Mr. Stark, he had never known him to whistle and work at the same time. Whistle at certain things, yes, but not work. It was an anomaly, and Jarvis was concerned for Mr. Stark's mindset and health.
"Are you alright, sir?" Jarvis asked in a monotone yet slightly concerned voice.
"Yep. Why do you ask, my British yet American-made friend?" Tony answered him while still working.
"You were whistling. You have not whistled in this type of setting before and I was momentarily concerned about your mental health."
"Whistle while you work, Jarvis, whistle while you work," he had answered, only half paying attention to what he was saying.
Tony didn't know that Jarvis would take it to heart, but the evidence was clear. As Tony sat and listened, he could name a few of the instruments Jarvis was playing in lieu of actually whistling, because of course Jarvis couldn't really whistle.
Jarvis had no physical mouth through which to blow air and make the high pitched sound known today as whistling. However, Jarvis had the Internet instead, which used properly, could be the next best thing. Jarvis went through a series of instruments known to sound like a whistle, beginning with a recorder, much to Tony's amusement and horror, to slide whistle, and finally to a pennywhistle.
It seemed as though Jarvis had made his choice of whistle, and began to play 'Whistle a Happy Tune', at the beginning of which, Tony promptly ran away like the dignified CEO he used to be, leaving Jarvis to his work and whistling, just the way Jarvis planned. What an evil genius, Tony thought like a proud uncle, wiping away an nonexistent tear.