Bit of a misleading headline, as I know it's obviously not the *only* time Jon has swore, but there's a fun story relating to the only time I really remember him doing so.

My grandmother is very old-school with this, & won't let any swearing near her. So, I was watching Jon on the TV near her because he never swears. So, I'm watching & not expecting Jon to do anything whatsoever, & then I remember him getting scared or something & him going "FU-"

It's kinda funny, tbh. Just the one time I was watching near my grandmother is the only time I remember him doing it. I can't exactly remember the content, though. I vaguely think it was Fallout 4, but don't quote me on it.