John Stamos was depicted as having the long hair mullet throughout all the seasons. In real life, he had changed his hair after the second season.
After celebrating the announcement of the fourth season ("Greek Week"), Candace Cameron gets frightened about her first kiss to a boy that her character, D.J. likes, and seeks advice from John Stamos and Lori Laughlin respectively. When she walks in, Lori's character, Becky, is telling John's character, Jesse, that because they are engaged, he is not allowed to flirt with other women. Jesse and Becky became engaged in the first episode of the fourth season, while D.J. kissed Kevin, the boy she liked, in the middle of the third season.
Candace Cameron is freaking out about her first on-screen kiss to her character's love interest, Kevin, which actually occurred in the "Full House" episode, "13 Candles", the seventeenth episode of the third season. However, when she goes to talk to Lori Loughlin about this, Lori and John Stamos are rehearsing a scene in which Becky is scolding Jesse for flirting with another woman, with Becky pointedly telling Jesse that they are engaged and he can no longer act that way. This is incorrect, because the characters of Jesse and Becky did not become engaged until "Greek Week", the first episode of the fourth season.