One other thing I didn't expect, but it might interest people to know: Some tickets are distributed to each person in the stateroom, like the Disney Junior Character Breakfast. For the meet and greets, I got one ticket per entire stateroom, i.e., one ticket covers multiple people. It makes sense, I guess, because for breakfast, they need to know exactly how many people they are serving. For the meet and greets, the characters greet each stateroom as a group, so they count by number of groups rather than number of individuals.
Each event takes place multiple times during the cruise, at least if it's a 7-night. The crew member will specify what date and what time you get. There will be another crew member checking tickets, so you have to have them with you. For the Princess Gathering, the crew member let us in about 10 minutes early. The people in the other stateroom we were with ended up going to another event so I gave him the extra ticket to give away; he mentioned that he had, in fact, been turning people away from the event. For Anna and Elsa, the crew member was a little stricter and would not let us in until the time on our ticket. I didn't know that they give everybody different times, so I was a little nervous when I arrived in the Atrium for the Princess Gathering and there was already a considerable line.
I never did get used to the lines on the ship -- I was always thinking, "I just left Disney World to get away from lines, and now this again!" Ha ha ha . . .