Her sincere but still completely off guess of it being upside down is fucking priceless, it's one of the scenes that stuck with me for literal years rent free. For me, it's when Katara is a little bit pissy at Toph for not wanting to go into the library and she's like "I've held books before, it doesn't do a lot for me." They went above and beyond the necessary during the desert arc, and also it added some drama to the pre-accepted Appa flight scenes.