Rollin Hand, posing as a Doctor, orders "5 cc's of Cordrazine" for Raymond Barrett. This is the same fictional drug with which Dr. McCoy is accidentally injected in the episode "City on the Edge of Forever." "Cordrazine" was named for Star Trek writer Harlan Ellison's pen name "Cordwainer Bird."
The characters are watching this episode, describe the portal as a "doughnut" and Gary says"Bones has gone through the "Guardian of Forever's time portal... To unfreeze time."