Question: What caused Fiona to turn back into a human?
Bishop73
3rd Apr 2018
Shrek 2 (2004)
Answer: Yes. Since the Happily Ever After Potion causes Shrek to become a handsome man and, according to the instructions, causes the persons one true love to also change into a different form, after Shrek became human, Fiona turned back into a human.
Answer: That was an unintended side effect of the "Happily Ever After" potion that caused Shrek to turn human and Donkey to turn into a white stallion; the reason it caused Fiona to revert to her human form is never really explained within the film.
Answer: It wasn't a side effect of the "Happily Ever After" potion, it was the main purpose of it. The potion turned the drinker of the potion and his or her true love into a more beautiful form. However, in order for them to stay in that form, they must kiss before midnight. Since Shrek and Fiona waited till after midnight, they reverted back. Donkey also reverts back. There was a script idea to show Dragon also change, but it was scrapped. However, we only see Dragon after the potion wore off, so she too would be in her normal form, since they didn't kiss before midnight.
Bishop73