Shakespeare's epicshrug◊ when asked where his pages are.
Chasing after Viola to find out about this Thomas Kent fellow, Shakespeare decides to climb up the rose vines to Viola's balcony. Just when audiences think we're about to see a re-staging of the infamous balcony scene from the play... it's the nurse who catches Shakespeare climbing up, and both are freaked out by the surprise.
During the opening audition for Romeo And Ethel the Pirate's Daughter, every would-be performer auditions by using the same lines from Marlowe'sFaustus, which annoys Shakespeare to no end.
Ned's reaction to learning about Mercutio's death.
How Shakespeare gets Ned to take the part in the first place.
Queen Elizabeth stopping at a puddle and looking expectantly at her courtiers, who quickly take of their capes, only for her to walk through the water anyway muttering "Too late, too late."
Pretty much everything involving the bloodthirsty young scamp, John Webster (who would grow up to become a writer of particularly gruesome tragedies), ESPECIALLY the scene where he tips off Mr. Tilney about Viola performing in drag:
Viola: Nobody knew.
Webster:(pointing at Shakespeare) He did! I saw him kissing her bubbies!