The AB Chrysalis

Original title: "The Chrysalis A-B-C". This was the only season two episode in which Tony Anholt doesn't appear (his name was mentioned once by Maya in the epilogue), a result of having been filmed simultaneously with Catacombs of the Moon (1976) (18 June to 6 July 1976, Nick Tate turning 34 on the first day of shooting, then Martin Landau turning 48 on the third day of shooting). According to Tate, during filming, England experienced a rare prolonged heat wave (which ended up lasting two months and causing 700 deaths), the temperature nearing 100 degrees Fahrenheit. He and Landau were stuck working inside spacesuits with temps reaching 120 degrees on set and at one point the studio's A/C ended up failing.

Koenig only draws four of the solar system's planets but the computer immediately identifies it as Earth; there are more than likely thousands of planetary systems with at least four planets.