re: Office etiquette scenario - is this mean..??

Reply All to office email is always a lose-lose situation.

1. Nobody wants that email.

2. Very few if any good can ever come from it.

You might stop by and say "by the way, I just want to make sure you know my response was a joke, and I figured you took it that way, but I just wanted to tell you in person"

I've seen people get fired over replys to a specific person and they were turned in by an observer on a reply-all distribution. It's not just the intended recipient you have to worry about, if ANYONE on the distribution finds it offensive you could be impacted if they came forward. This seemed harmless so I seriously doubt it is anything to worry about, but I generally leave my "hilarious" questionable sarcasm and jokes to verbal only in the workplace so I ensure it comes across as I intend, it is targeted, and I people tend to be a little more brash behind the keyboard so it is easier to avoid saying something inappropriate.

Too risky these days.