Gertrude (Marge) – Knocked herself out with a mace to avoid cleaning up the mess of bodies
Polonius (Chief Wiggum) – Killed when Hamlet stabbed him who thought he was Claudius.
Laertes (Ralph Wiggum) – Unintentionally stabbed himself when practicing his duel with Hamlet.
Ophelia (Lisa) – Jumped out a window and landed in a moat where she drowned.
Rosencarl and Guildenlenny (Carl and Lenny) – Died when they high-fived each other after being covered in poison.
Professor Frink wasn't with Odysseus' crew when they were turned into pigs by Circe. He was last seen when they went to the Island of Sirens that his glasses were broken when he saw the Sirens and crying out loud "Save me from the ladies".
A deleted scene in the Odyssey segment featured the cyclops Polyphemus, portrayed by Comic Book Guy and an extra scene with Patty and Selma as the Sirens where Patty's seashell bra tries to crawl away.
The title is a reference to the stories' copyright that have either expired or never was copyrighted to begin with. This means producers are allowed to create the stories with Simpson character without prior consent nor royalty fees. The only exception of the theme to the song Ghostbusters, however, it's not mentioned if any fees were paid.
The title "Do the Bard, Man" is an obvious amalgamation of one of William Shakespeare's famous titles, the Bard of Avon, and Bart Simpson's famous tagline, "Do the Bart-Man."