Young Sally has some specific tastes about costumes but it makes sense with context. If you didn't live in the ye olde days of big blocky TVs, look up "rabbit ear antenna" for info. Some of the best moments Sally has had is watching anime while being near Tobi. It's only fitting that the thing she would like to dress up as is something that has made countless good memories for her. Her parents might not understand her thoughts but at least it's simple to create for once.
