Pat Priest's first appearance as Marilyn, after Beverley Owen's departure. She only appears in the coda and does not have any lines.
The opening credits were re-shot when Pat Priest replaced Beverley Owen as Marilyn. In the original sequence, Herman comes last; now he comes first.
Grandpa, in his magic show, uses a steamer trunk that previously belonged to magicians Thurston (known for performing a floating lady illusion) and Houdini (noted for his sensational escape acts).
The opening credits were re-shot due to Pat Priest replacing Beverly Owen as Marilyn. Unlike the rest of the cast, Priest is seen only from the side and does not face the camera. This was perhaps done to keep audiences from noticing the change.
Herman is reading (and enjoying) "The Murders in the Rue Morgue", a short story by Edgar Allan Poe published in 1841. According to Poe's biographer Kenneth Silverman ('Edgar A. Poe: Mournful and Never-ending Remembrance', 1991), it's considered to be the first modern detective story.