Marge can't trick-or-treat. Do you mean Lisa? Because apparently quite a few players have had issues with her disappearing. A few other characters, too, but most characters have associated buildings that can be stored to bring them back, while Lisa can't be stored.
If it is Marge that is missing, store Moe's and then place it again, and she should appear.
Man it really sucks that sending anyone trick or treating can potentially make them disappear. hopefully EA fixes this soon
I am using ipad3 ...
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