Agreed that Kelso should have stayed a regular.
Gary Lockwood is one of the coolest guys you could ever meet. He happily chatted away with me for nearly an hour, putting up with my endless questions about, what, to him, was a week's work 40 years ago. I wanted to hear about Trek, he wanted to hear about Australian girls and beaches
This episode is an 8 for me. Endlessly re-watchable, with the stars of the outing being Shatner, Lockwood, Kellerman and Carr.
It's nice to see Sam Peeples getting the credit he deserves in guiding Roddenberry through the world of SF by contributing ideas and lending Roddenberry his SF library in Trek's earliest days.