Since Peter started coming to Stark Tower almost everyday Tony has started noticing JARVIS saying things he was very not programmed to say.

A good example being on a Tuesday Tony asked JARVIS to tell him the date and JARVIS says 'Its the 23rd of March. Its a Two Taco Tuesday'

But Tony doesn't realize exactly until a month ish later when he notices just how odd JARVIS is speaking

It was exactly when he said 'Its a Mopey Mood Monday my dude bro but at least its only raining in the brain today'