Granny was chatting with on the phone with Donatello about pizza. This is a reference to the Teenage Mutant Ninja Turtles (1987), who are known for their love of pizza and one of whom was named Donatello. Sean Astin, (Gomez Addams) son of John Astin, would voice Raphael in Teenage Mutant Ninja Turtles (2012).
Fester proves he is bright by charging a lightbulb. This was a classic gag from The Addams Family (1964) where Fester would light up a lightbulb by putting it in his mouth.
Pugsley asks Uncle Fester's help in solving the mystery. This is a homage to The New Scooby-Doo Movies (1972), where the Addams Family made a guest appearance and aided Scooby and his friends in solving a mystery.