Willo The Wisp can refer to one of two series, but when one refers to the show, what first comes to mind is a delightfully odd children's programme from the early 1980s, written and directed by Nicholas Spargo and hand-animated by a small team in England.
It's a series of short episodes, maybe five minutes in length or so, about the denizens of Doyley Wood (an actual forest near the director's home) which most mishear as "Doily Wood", fitting in with the show's general aesthetic.
The story is narrated by Kenneth Williams, who also does all the voices. Williams, though famous for being good at speaking, isn't able to change his voice enough so that it sounds like dissimilar actors - we're not looking at an expert impersonator like a Frank Caliendo creating remarkably different voices. But the effect is charming, because Williams changes up accent and diction enough to portray a distinct character in each instance, but still be familiar in all roles. The effect is rather similar to an expert storyteller for children reading a book and "doing all the voices".
The use of a narrator also allows for significant or expensive parts of the story to animate to be given by exposition instead, and allow for a rapid "moving-on" of the story. Given that the narrator is a supernatural creature (and also a charming caricature of Williams) it is an omniscient narrator, knowing the thoughts and motivations of all characters.
The primary protagonists of the story are Mavis Cruet, an obese fairy who's not terribly good at magic and who is too heavy to fly. She has prominent front teeth with a slight gap and is clearly plain looking, in contrast to the willowy, supremely beautiful fairies typically used in children's television. The fact that she has an unglamorous name like "Mavis" makes her a far more relatable, homey character. She often tries to lose weight (in the politically incorrect days of the early 1980s, we see her doing jumping jacks with resulting crashing sounds and shaking the entire forest), and wishes she was better with her wand, but she has a strong moral core (albeit not strong enough to resist once going to the primary antagonist for help) and a genuine empathy for everyone, even going so far as to say "poor Edna" when some calamity befalls her. She speaks in a high register, short of falsetto, and cries by literally saying "Boo hoo, boo hoooooo" in a soft vibrato.
Her best friend, Arthur the Caterpillar, is her opposite. Coarsely voiced in a tenor register, he typically has to come to her aid or comment on her attempts to improve herself. Clearly a Cockney and based on Kenneth Williams' impersonations of his own father, he's not above putting down anyone he disagrees with, even going and squaring off with forces beyond his control in order to help Mavis. He's orange with a white face and a wispy top-knot he refers to as "me feathered happendages".
The primary antagonist is Evil Edna, the witch, a heavily wrinkled face inside an old school wooden television cabinet. With a grating voice in an alto register, she refers to everyone as "dearie" even as she's using her bendable antennae to cast spells, usually for evil aims. Irascible, bad tempered, mean and generally miserable, she is usually one to avoid because of her power. And yet, Arthur is often able to get the better of her.
Rounding out the cast is a prim bookwormish blue cat named "Carwash", which is Williams speaking very very primly and quickly, and "the Moog", a small ugly tan puglike dog with near-zero intelligence and a slurred broad-vowelled speech to match. Later on in the series we meet "the Beast", the only creature NOT transmogrified back into its original form somehow by Evil Edna. Apparently once a prince, he angered Edna by saying the programme she was playing (in other words, her face) was horrible, causing her to change him into a sasquatch-like, sad-eyed mammal as revenge, voiced by Williams as an upper class twit with a decided inability to pronounce the letter "r".
The strongest and most dissimilar voices beelong to Arthur, Edna and Mavis, so they compose the majority of screen time and speech.
To give you an idea of a typical story: Arthur, Carwash and the Moog are walking through the forest one day and take shelter under a tree because of rain. When they realize it's actually raining FROM the tree they're sheltering under, they realize that Evil Edna has changed Mavis into a weeping willow for some unknown reason, and the "rain" is her tears. Arthur, intent on getting Edna to undo her magic, sets off to find her and is accosted by a salesman enroute, who shows him an increasingly nonsensical array of items to buy. Arthur does however, light up when he sees a "pong" game that plugs into... a television set. With a devious idea, he attaches it to a sleeping Edna and wakes her with the order to change Mavis back to being a fairy. When Edna threatens to turn everyone into frogs instead, she suddenly switches to showing a game of pong. Arthur switches off the machine causing her to angrily ask "what was that?" and the moment another threat is imminent (and a beautiful censoring of a line adults watching would have finished in their heads) Arthur switches it on again. After a few seconds Arthur turns the machine off in order to get her back. To rid herself of the indignity and the extreme discomfort and disorientation of being turned into a video game, she reverses the spell and then disappears before Arthur has a chance to change his mind and keep playing. Yes, it is that delightfully weird.
A new series was commissioned in the 2000s after Williams' death, which is the second possibility with which to use the title - but the effect isn't the same.
I mean, Kenneth Williams had a very distinctive voice, and therefore any other attempt to copy the characters' affectations would be ruined by anyone who was charmed by the original. Evil Edna's design has changed to a flat screen on a rolling stand, as opposed to a wooden TV set with stumpy footed legs. Mavis has been slimmed down considerably and made less plain, but she still cannot fly, and the fat jokes are absent from the new series. But the biggest changes are that the scripts aren't quite as delightfully weird as the old ones were, and the visual look is simply too clean. There was a nice softness about the original series - it was shot on film, and the palettes used were decidedly in the earth tones and warm colors. The new series is done by computer direct to video and has far harsher blues and greys, which detracts from the childhood bonhomie of the original. Edna looks far more sinister gliding around with a stark blue case and with her scrunched up expression in sharper focus, rather than the softening peculiarity of her gait on four stumpy legs. The framing tends to be different as well. Rather than have the story drive the narrative, with characters facing each other, the animation is far more "in the round", with people interacting more cinematically than the original.
It's hard to explain the difference, but it's jarring. The original was just enough animation upon which to hang a storytelling, and the new one has so much animation you're watching a cartoon where they were too cheap to hire different actors to do the different voices.
Apparently it was used in the United Kingdom and some Commonwealth countries as little bits of "filler" between shows, and some dedicated lovers of the series have put many episodes on YouTube. It's the kind of show where you actually want to sit someone down with a blanket and some cookies and treat it like the old school narration that it is. God bless the British, and the dearly departed Williams, for being so bizarre.