My coworker sarcastically called me "boss"

Actually he wished me a "Happy Boss's day". I am not his boss; in fact we have the same title and position, though he has been there over 25 years and I have been there 10. What should I make of this? Honestly it pissed me off a little. I won't defer to him, so I get this sarcastic bullshit? 10 years is plenty long enough to know what I am doing. And I am sick of being walked on all the time (this guy treats other people generally like crap- so much so that when we have interns we will not let them work alone with him until we know they can stand up to him), so I am becoming more assertive. Well, I cannot stand this guy and wish he would retire already. He can barely do the job but thinks he knows everything and the world revolves around him.

I long for the day I can tell him to fuck off. I guess it will be when one of us leaves, preferably me.

He wants to be the boss thinks he SHOULD be the boss and obviously feels like you are the same and behaving in the same way. Incapable of understanding others POV, sounds like to me. I have encountered the same type, in some sense in my career except they were the brown nosing type and couldn't understand why I actually would criticize decisions when I thought they were wrong-horrors!

when one of the other techs eventually retires. Assuming I am still around, that is. Which would make for an uncomfortable situation no matter who gets it.

A little comment like "Oh, you heard about my promotion. I thought that was going to be kept quiet for the next few months."

You'd have his head so screwed up, maybe he'd quit!