All meals, breakfast, lunch and dinner.
I have seen many posts where people have expressed disappointment that their server "wasn't into it"......I personally think that has more to do with how the guests react than with the server not being into it....same thing as 50's. I have noticed servers treating different tables differently (most often at 50's, but I'm sure the phenomenon is the same everywhere)....I really think the server "feed" off of the guests, and if the guests are really into it and playing along and seem to want it, then they keep it coming....but the guests who just kinda sit there don't get teased nearly as much.....maybe that's practice on the server's part to read people well enough to know when they aren't the type that want it....and maybe sometimes they misread and those are the families complaining. Don't know, but that makes sense to me.
No matter what restaurant we go to, Disney or not, my girls are always engaging servers in small talk (and sometimes boring the poor server I'm sure)...it's just their personality. THey haven't quite figured out that the whole world doesn't want to know about their upcoming trip to Disney, or whatever else is happening in their life, lol. So I'm sure it's very obvious to DIsney servers that they're ready to party! And sometimes I think we get it going to much even.
THe first time we went to 50's, we specifically told the hostess before we were seated that we hoped to have a lot of fun talking to our long lost cousin (this was a tip I read on DIS)......so that hostess knew we hoped to get a server with a lot of playfulness. The next time we were with friends and we forgot to ask, but still got a playful server. WCC we never asked, but I also don't recall seeing any servers NOT being playful, so might not be necessary.
If you go in with a "let's have silly fun" attitude, I'm betting you'll have a grand time! If you go in expecting to sit there and be entertained, you may be disappointed....the servers want to INTERACT not entertain. Entertain is passive for you, but Interact means you gotta give back as good as you get!