MK and DAK have formal "Rope Drop Ceremonies" that involve several Disney characters with "speaking roles" (on a recorded soundtrack).
MK has the "big one" that involves singing and dancing, a "chosen family", the steam train, and many favorite characters.
These are USUALLY performed every morning (but no guarantee, especially at DAK). When its an EMH morning at a given park, the ceremony is usujally performed only for the EMH guests and not for the "regular hours" guests an hour later.
Epcot has spradically had a few characters at its rope drop (but I have yet to witness it in-person).
MGM has a recorded announcement and no characters.
All parks MIGHT have a "chosen family" (or two) that leads in a countdown at the front gate before guests are let through the turnstyles, but this is not the formal "rope drop ceremony".
Guests should be at the front gates of any park by 30 minutes before the scheduled open time (EMH or regular) to be in a better position to see the bigger ceremonies.
(The formal ceremonies' actual running time is about 5 minutes.)