It's the first of two OVA sequels to the Hare+Guu TV series, the second being Hare+Guu Final. It's more rapid-fire than the TV series and sometimes also more manic, but it has a surprising variety of stories and personallly I found it funnier.
I'll recap. Hare is an eleven-year-old living in the jungle with his lazy, happy-go-lucky mother Weda and a Lovecraftian extradimensional entity, Guu. Everyone else thinks Guu is a pink-haired little girl with a deadpan expression. Hare knows she's a monster, capable of rewriting the laws of time and space to torture him and/or have a laugh at the expense of us mortals. The two hang out together, although that's mostly because Hare doesn't have access to technology that would let him run away fast enough.
This is funny. I liked it. Some reviewers loved it, though, and appear to have thought it was funnier than I did. I suspect this might be because of the English dub, which I believe is well-regarded. There are a few rather good English dubs of comedy anime and it's not unknown for them to be better than the Japanese originals. I should also note that the 2007 American Anime Awards nominated Jennifer Sekiguchi for "Best Voice Actress in an Anime Comedy" for her work as Kirie Kojima in Girls Bravo and, yes, as Guu in Hare+Guu. (Her real name's not Sekiguchi, though. She's really Stephanie Ru-Phan Sheh and she speaks English and Mandarin Chinese.)
The people who thought the TV series was stunningly brilliant seem to have thought this OVA series wasn't as good and, perhaps as a result, the second OVA series (Final) to date hasn't been licenced for an American R1 DVD release. Me, I slightly preferred it. Not enough to start a fight over, but it made me laugh more. It's basically more of the same comedy, but with a few points worth noting:
(a) A higher density of story ideas. You'd be surprised to get this rate of turnover in TV anime. Each episode is split in two, so this six-parter is really twelve mini-stories, each of which could have supported a full episode. I suspect this is more in the vein of the manga.
(b) Extreme overreactions. Hare's bogglings when shocked, alarmed or homicidally angry at times made me laugh out loud. The first episode in particular is like every cliche you've ever imagined of anime to make Looney Tunes characters seem meek and restrained. It was too much for Tomoko, I'm afraid, but it gets toned down in later episodes. (To some degree.)
(c) Plot. There's as much as in the TV series, I think. Weda gets pregnant and married.
(d) An interesting variety of stories. The child-hating Godzilla rage monster (i.e. the new teacher) in 1/1 with romantic yearnings is hysterically funny, but in a straightforward Wacky Anime way. The transmogrified talking cockroach people, on the other hand, are faintly sad and disturbing. (Thanks, Guu.) Favourite characters get a return visit, so we enter the Village Elder's Dreams of Chest Hair and there's a brilliant horror episode with Grandma Dama. (This is a mad old woman with a mega-afro who thinks anyone with white hair is her late husband. She can also come at you like a charging bull and moves like a cross between H.R. Giger's Aliens and Sadako from The Ring.)
We even have stories that explore Hare and Weda as characters. Those were good. I'd have liked more of Gun-Crazed Robert and perhaps of Guu herself, but what the hell. This OVA series exceeds my expectations in how many stories it has and to how many characters it gives spotlights. I'm nuts in particular about Grandma Dama. She's almost painfully funny in both of her appearances, especially when fighting.
They've changed the music, by the way. The opening theme is simply a rearrangement with new lyrics, but the closing theme has broken my brain. I think it's brilliant and repellent. We have a cool song, faintly disgusting visuals, Cute Guu at her cutest and then immediately afterwards becoming Scary Evil Guu, using Hare as a shotput and leering at the camera.
In short, I liked this a lot. It made me laugh, sometimes hard. I like its unexpected variety, such as an anime parody with Marie and a Back to the Future episode. I like the character exploration and development. I like the hint we get in episode six that Guu might have become infected with a smidgin of humanity, deep down. "You must like to meddle in other people's affairs." Then we're reminded that what we were watching was a story-within-a-story narrated by Guu herself and hence likely to be all lies. It's a shame that Hare+Guu Final doesn't have an English-language DVD release, but that's not going to be stopping me.