When Dr Lecter (Mads Mikkelsen) has Dr Bloom (Caroline Dhavernas) and Dr Chilton (Raúl Esparza) for dinner, he says to Dr Chilton "it's nice to have an old friend for dinner". This is a direct reference to the end of The Silence of the Lambs (1991) where Dr Lecter says to Agent Starling (Jodie Foster) that he's "having an old friend for dinner", meaning an unsuspecting Dr Chilton who has just landed on the island.
Hannibal (Mads Mikkelsen) serves Dr. Bloom (Caroline Dhavernas) and Dr. Chilton (Raúl Esparza) the tongue from a lamb, and he mentions that it was a "particularly chatty one". Removing the lamb's tongue would have rendered it silent, a clear in-joke to The Silence of the Lambs (1991), the movie that the character Hannibal is most famous for.
The title, "Entrée", is French for appetizer. The word has been borrowed into English in the sense of a main course, but its original meaning is the opening course (literally, the "entrance").