The Doctor wields a gun and throws punches. The tone of this story sits awkwardly alongside the other early Tom Baker stories. Douglas Camfield liked his military / action stories, as well as those Euston Films crime dramas - and it feels like he's imported that sort of feel into this.
The Doctor far too quickly opts for the RAF bombing solution - when he has usually been scathing of military responses.
Criticised by Mary Whitehouse for recent violent incidents in the series, Robert Holmes claimed it wasn't as if they were teaching kids how to make Molotov Cocktails. What do we see being made and used here...?
The Krynoid pods travel in pairs, and can be located only a few feet from each other despite having been buried for years. We don't know how long - there's talk of when Antarctica was covered in vegetation thousands of years ago, but that's when the scientists think the pod is native. It may only have arrived days or weeks ago - especially when it is found so high in the ice layer.
Irrespective of how long they've been there - how do they manage to retain such close proximity? From an evolutionary standpoint, why pair up when the adult Krynoid can self-germinate? Wouldn't two of them actually compete, with only half the available food supply for each? Or is one simply a back-up, in case the first is destroyed?
The Doctor knows enough about them to find the second pod - yet he doesn't know anything else about their origins (he only speculates on their planet being volcanically active) and never tells us anything useful like why - and how - they travel in pairs.
By digging up the second pod, the Doctor directly triggers all the death and destruction of Episodes 3 - 6. If he had just left it where it was, and quietly collected it later on, only the base personnel would have been killed (as a result of their own actions before he got there anyway). Scorby and Keeler would have still turned up, but may have simply left empty-handed, or with the opened pod for Chase at best. They might still have blown up the base to hide their tracks, but everything that happens in England is down to the Doctor.
Major Beresford. Just how long has he been serving with UNIT that he ridicules the Doctor's warnings?
If John Levene had been available for this story, would he have taken the part Sgt. Henderson played - and if yes, would he have been killed off in the compost making machine?
At one point the Doctor puts Sarah's life in jeopardy by leaving her in the grounds of a mansion full of insane millionaires, mercenaries, alien plant monsters, and a trigger-happy private army, whilst he goes to make a phone call. Er, surely it should have been the other way round?
When he writes the cheque for Miss Ducat, Chase rips two cheques from his book instead of just the top copy he has signed. That's what you get for wearing black leather gloves all the time.
The one everyone mentions - the TARDIS arrives at the South Pole and Sarah says the Doctor forgot to cancel the co-ordinates, despite the fact that they arrived in Antarctica earlier by aeroplane. This can be got round if we assume the Doctor was going to use the TARDIS, then changed his mind to use conventional transport. However, he's in a hurry to get to the pod before it germinates - so why mess about with 'planes?
Sarah's breath clouds in England, but not at the South Pole. She's in a bathing costume, yet she stands around joking with the Doctor for a while. Mind you, she has form in this area - having spent ages in her swim suit on Exxilon before finally changing into something more practical.
Something which went wrong behind the scenes on this very sequence - the TARDIS prop collapsed on top of Baker and Sladen, prompting the building of a new Police Box for the start of Season 14.