 The scene when Shrek, Puss, and Donkey walk in on Fairy Godmother  while shes pouring potion ingredients into a large cauldron is a  nod to a scene in Disneys _Little Mermaid, The (1989)_ (qv) when  Ursula is preparing the spell to make Ariel human.  Jennifer Saunders (qv) (who voices the Fairy Godmother) had  originally auditioned for the role of Ursula (but was turned down)  and was cast for her role in Shrek 2 after  Steven Spielberg (I) (qv) heard Saunders performance on the  audition tape.