Castle says he was so upset about John Lennon dying, he stayed in his room for a week. Nathan Fillion was about 9 when Lennon was killed.
Castle asks a suspect if he did a "Hulk smash" on one of his band mates. This is a reference to the Incredible Hulk, a popular Marvel Comics character whose catch phrase is "Hulk SMASH!".
When McGinnis says he "took a third rate Miley Cyrus and turned her into the next Gwen Stefani", Miley Cyrus now has more nominations and awards than Gwen Stefani, including a diamond single.