Saturday Night Live. My curfew in High School was before the ending of SNL, so getting to watch the whole show was really being up late.
Of course, like so many things, it seems that the SNL of my youth was better than it is now, but I think that is just as much on me as it is on them.
One thing I've always enjoyed were the SNL shorts. These filmed bits started creeping into the "live" show decades ago. I fondly remember Mr. Bill at a time when kids my age would say, "Mr. Who?" Of course these same kids didn't have a clue who Dr. Who was, but that is a different issue for a different post.
I didn't stay up to watch SNL....I'm getting too old, it isn't "live" in my time zone anyway, and it's unfair to my wife who has to get up early AM to go to work. Luckily for me NBC likes to put the shorts online so I can see some/all of the show later.