You need to be in the line at least 30 min before the show, but I'd be in the area before that. Once they start letting the package people in, you'll want to be in that line. After that line is empty, they let in standby and your "seat" will no longer be saved.
The pickier you are about what area/seat you sit in the earlier you need to go. The more popular the narrator the earlier you need to go. As sharonabe said, at least 30 min before. I was there for Neil Patrick Harris and got in line as soon as the prior show was done. Holy moly what a line.
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