The TV series was based on a series of books by Colin Dann, but a lot more people know about the TV series than the books. Notably in the books Owl, Weasel and Kestrel were males - but they're more commonly thought of as females because of the TV series.
Just as well known at the time was the magazine spin-off: "Farthing Wood Friends" which had a catchy enough name that children often used it when they were referring to the show, and it ran to over a hundred issues. It's been forgotten because, well, magazines don't go into syndication.
If one read the Farthing Wood prequel stories (published after the initial book series), they'd discover that Fox's father was one of those responsible for the eventual destruction of Farthing Wood by banishing a troublesome protected species of otters. With this in mind, it's possible to interpret Fox's character as one who resigns himself to protecting the animals, out of his own guilt for what his father caused.
Friendly in the TV series. Did he rat out Charmer to Fox just to make himself seem like the better cub or did he do it out of concern for her safety? Considering his other sister Dreamer was killed by Scarface, the blue foxes' leader Friendly not wanting the same to happen to Charmer could explain his hatred towards the blue foxes.
Season 2. One half of the base loves it for its Darker and Edgier tone, subverting a lot of typical children's show tropes and introducing a lot of good characters like Bold, Scarface, Ranger, Charmer etc. Others don't like that it renders the end of Season 1 meaningless - with several immediate deaths among the Farthing Wood animals - Mrs Fieldmouse going out within the first few minutes of the Season 2 premiere. Some find that the season is simply too dark to be enjoyable.
The third season subplot involving Weasel, Measly and their children, Cleo and Fido moving out of the Park is either seen as a plot that is very enjoyable and funny or is annoying, meanspirited, and just as bad as (if not worse than) the other kinds of Filler in Series 3 since it adds almost nothing to the Rat Invasion plot. Doesn't help at all that Weasel Took a Level in Jerkass, particularly with her treatment of Measly.
Arguably Bold. Definitely the most complicated character of the cast with the most complete arc.
Adder as well for the same reasons.
Her mate Sinuous: Many fans either love him for his design, his relationship with Adder, his overall character, or all of the above. Even those who despise Season 3 find him to be one of the few redeeming qualities about it.
Friendly has his share of fans too. Even amongst those who find the foxes in general to be overrated.
Kestrel is very well-liked too, to the degree that many are annoyed at her unexplained disappearance in Season 3.
Evil Is Cool: Scarface is probably one of the coolest (and scariest) villains in children's cartoon history.
Bully the rat in Season 3 is widely considered to be nowhere near the Big Bad that Scarface of Season 2 was, due largely to being incredibly watered down in his depiction compared to his book counterpart, being an ineffectual, laughable villain with zero menace rather than a legitimate threat.
Dash is this for some, though ironically she's not replacing a character per say. She's the daughter of one of the original Farthing Wood hares who's inexplicably gone in Season 3.
Season 3 tends to be the least well-regarded amongst fans of the show, largely due to the change in animation style which many fans find it to be a massive downgrade, the greater emphasis upon slapstick comedy over drama, and a less solid plot (along with much more Filler than the first two seasons combined). Season 3 also drops a number of well-liked named characters without as much as an explanation (presumably to keep the cast smaller).
The first season in Norway. The episodes were shown out of order on repeat making it seem they vere trapped in the same woods forever with no forwarding in plot and so many weird dialects (they were from the same place yet spoke different dialects, even within the speices families) in the dub that one didn't understand half the dialogue. It ended up being a surreal experience that only led to Darkness-Induced Audience Apathy due to being too gloomy and depressing.
Season 3 drops a lot of the side characters presumably to keep the cast smaller. This has the effect of getting rid of a lot of Farthing Wood regulars who had been there since the beginning - especially Kestrel. Admittedly she (or he in the original) was Put on a Bus in the books too. Friendly made one appearance in Season 3 and then abruptly vanished.
It happened in Season 2 as well. Mrs Fieldmouse is immediately mistakenly eaten within the first episode, and the voles and hares are Out of Focus until their eventual deaths.
Unintentionally Unsympathetic: For some fans it's really hard to feel bad for [[spoiler: Bold at the end of the episode The Feud Begins when Fox scolds him. Had Bold felt guilty for getting Fox and Friendly captured by the Blue Foxes and tried to apologize then he would've been easy to sympathize with; but instead he shows little to no remorse about his actions and doesn't even try to say sorry. He does at least suffer Break the Haughty once he leaves the park.
Poor, poor Bold. Whilst he may have started out well in life, once he left the safety of White Deer Park he was shot, crippled, injured by a snare, hunted, and would have starved if it wasn't for Crow and Whisper. Then, once he finally thinks life is turning around, Whisper insist they return to White Deer Park so their cubs can be born in safety. He's subsequently attacked by dogs, and if that wasn't enough the journey back is too much for his weak body to endure and he dies before his cubs are even born.
Mrs Pheasant, who dutifully does everything for her husband only for him to constantly complain. It's clear that she tries to avoid being The Load in spite of her husband. After she's killed by the farmer, her husband has a Heel Realization shortly before his own death.