Roots: Sarah says 'Oh, so we're off course. Lost in space!'
Goofs: We hear some strange, loud noises in space [although given it's an audio adventure about big bangs, perhaps this is excusable].
Technobabble: There's some malfunctioning of the TARDIS' relative dimensional computer [which, the Doctor explains 'means that the steering's gone haywire']. Other features include a chronometric astrometer, while cosmo-retrozine enables the TARDIS to free itself from the proto-Earth's gravitational pull.
The 'compressive telesight' "lets the events of millions of years pass before you in minutes".
Double Entendres: 'You know how tactful one must be with the low continuum resolution.'
'Look, Sarah, look at that enormous body; we're held in the pull of it.'
Dialogue Disasters: 'At this speed we're getting loster and loster, thousands and thousands more miles every second.'
'Insolent ignoramus! Take that!'
Dialogue Triumphs: The Doctor shows off about his travels 'Everest? Stalagmite!'
Continuity: Given her longing to see the place, it seems to have been some time since Sarah was last on Earth, or at least in her own time. The TARDIS has a bubble-like two-person capsule which enables both the Doctor and Sarah to witness the creation of Earth - it requires 'atmosphere injection' [probably some form of life support, given that after 'injection' a humming sound can be heard].
Megron is High Lord of Chaos and Chief of the Carions, Lords of Chaos and 'enemies of the Time Lords down the endless ages'. Presumably they have less power than the Time Lords now, as the Doctor easily defeats him by Telepathic Will Deployment [perhaps this is something like the mind-wrestling seen in 'The Brain of Morbius'?].
Location: The TARDIS, and Earth's outer atmosphere (or thereabouts) 4,500 million years before present, and various points (three further stops 'millions' of years thence) afterward.
The Bottom Line: 'Bye bye, Megron, bye bye chaos, bye bye! Say "Bye bye", Sarah'.
Weird. And educational, probably. On the whole the episode, running at just over 19 minutes has a rather inconsequential feeling to it, but given the lack of real plot, it's probably just long enough. For an adventure that has as much to do with Doctor Who's ongoing story as Search Out Space, this is best taken at face value.