The only episode of the series in which the episode's title and writer and director credits are displayed in black letters against a white background (the fireball created by Will's failed "message in a bottle" rocket). The usual practice was to display those credits in shadowed white letters.
The scanner image used in The Derelict (1965), in Welcome Stranger (1965), and in Invaders from the Fifth Dimension (1965) is used here again, specifically the white on black variation that was first used in Invaders from the 5th Dimension. It previously and respectively represented an enormous spaceship, a small one-man Earth ship and an inter-dimensional alien craft; this time it represents an entire planet.
Don and Judy continue their "friendship" with one another. The night before Don's departure in the revamped reactor chamber ("the raft"), Judy goes into Don's room wearing a robe of sorts. She wants to say "goodbye" the night before he departs because waiting until launch time would be too difficult. Also, as a "goodbye" gift, Judy gives Don an audio tape that she made for him, asking him to wait until later (presumably during his flight) to listen to it.
This is the first episode where the Robot cracks a joke. Dr. Smith asks it if it's familiar with the bag of wind (a balloon) outside. It replies that it's familiar with the bag of wind right here. Dr. Smith confirms the Robot is referring to him.
When John and Maureen are seen searching for Will in the Chariot, with Maureen driving, this is actually footage originally from Invaders from the Fifth Dimension (1965). Even some of the dialogue where John says to Maureen, "Let me drive for a while" is identical. Long shots of Don flying with the jet pack also show previously used footage.