As a recent obsessive Whovian for the classic years of Doctor Who particularly the Pertwee era is my absolute favourite due to the fact there's some smashing frilly shirts and velvet jackets and the cape, oh the cape; it actually flaps when he runs!
I haven't heard a great love for this episode but for me I think it is a stunning story which involve a catfish like monster which actually isn't a monster at all, and there lies the beauty of this story.
The story begins with the Doctor and Jo ,who for me is one of the most unique and brilliant companions ever, at the lab where a mysterious ball like object appears from the time lords but which can only be opened by the person it is meant for. A funny moment for me was when Jo looked at it and said;
The Doctor replies, "No".
"Bomb"? She asks.
To which the Doctor becomes a little irritated and hastily walks off into the TARDIS as it's light begins to flash which tells the Doctor he will be taken to where to the person the object belongs too.
I think this comedy element really encapsulates Jo's character as she just automatically thinks that any mysterious object that falls into the hands of the Doctor could be a bomb.
The TARDIS lands in the 30th century on a planet named Solos where the Marshall becomes the obvious evil and insane one.
Additionally, I think the actor who played him showed real menace and just looking into his eyes I could see a real arrogance and viviousness behind them.
The story behind the Mutants I think was an intelligent and thought out concept which were able to change the audience's opinion of them and show that not all the aliens the Doctor encounters are evil or have an agenda.
These rather cute little critters were in fact Solonians who had mutated too quickly and therefore were not able to fully evolve into their superior selves which is what happened eventually to one the citizens; Kai played an American actor who manages to pull off his English accent quite convincingly.
As Jo is once again tied up, I thought her fake collapse to gain the upperhand with the guard was hilarious as she quickly grabbed his gun and said, "Right"! in a rather annoyed but authoriative tone.
Concludingly, the Doctor and Jo's retreat was I think typical Doctor style to make up a rather unconvincing lie to ensure their swift escape.
The Doctor and Jo's relationship I think is very playful and jokey in this episode and the Doctor appears to act like Jo's father in a way as he always appears incredibly protective of her and seems to hold her hand a lot which is why I love this era of Doctor Who; the Doctor has a unique relationship with his companion and they get to play with lots of amazing stories!