Both of these come from the same studio, so they have a lot in common... most noticeably the weird frog and the quirky sense of humor. It borders on being ridiculous, so I don't suppose it's for everybody, but if this sort of humor suits you then you're in for a treat.
It is VERY similar to Negima!? in many ways. It was made by SHAFT, features the same craziness that each one offers, even has the whole 'kid teacher' thing going on each with its own ways on making it work out.
Both shows are from the same studio, SHAFT, so they share quite a bit in terms of humour and style. Zetsubou Sensei has much more dark humor though, and a more distinct artistic style (in some ways similar to xxxHOLIC). Negima is a bit more random, and focuses a little more on magic and jumbled relationships and such.
Harems where the teacher is the guy and all or the majority of the class is girls.
I know your not suppose to recommend sequels or related series but I think this is a special case because Shaft did the animation production for both Sayonara Zetsubou Sensei and Negima!? which gives them a similar feel.
Just watch the opening theme for the two series, you will see what I mean.
Both have stories about a boy getting surrounded by girls. The girls in Tenshi no Shippo may be animals but they always show up as young girls. In both, the girls fight over the attention of the main character.
Both have magic, male main characters that have a lot of women that fall in love with them, a good bit of comedy mixed in, and make you feel a bit ease while watching it. Neither take them selves to seriously and are just fun to watch. Both have action, comedy, and romance.
Both are about a guy that has a harem of girls trying to fight for his affection. They all have different characteristics and are pretty much stereotypes of girls we would normally see in shows like this but not all of them are romantic. In fact, both have girls that just want the main character to be like a sibling to them.
An adorable kid with strong powers turns up and ends up helping/having to give his new friends/students powers. Both have action and comedy and center around some sort of magic. The main character loves his friends/students, is very selfless, and likes to smile.
If you saw bakemonogatari you will realize that there are very similar scenes, they share some themes (Magic, vampires, etc.) are not the same type of series, but the dynamics of the narration and some scenes are very similar
Both animes center around harem and romance with the similar aspects of negima being magic and seirei being a mixture of demons with magic but personally i don't think the magic aspect is the same as negima both animes include kissing being how you make a contract and a similar dilema being they have to get stronger and both in the same environment being a school differances in negima he is a teacher and seirei he is a student you will love negima if u liked the harem situation but if you liked the magical aspect of the girls becoming like magical girls then i don't think seirei is the anime for you read more
The way ef, presents it's animations is very similar to that of Negima. The difference is their storylines. Compared to Negima!?, which uses the animation for more of a magic/adventure (Harry Potter-like) anime, ef uses these animations for more of a cross between romance and drama (similar to that of Kare Kano.)
Because they are both directed by Akiyuki Shinbo and produced by studio SHAFT, they are very similar in style. -MOON PHASE- has a young girl who makes a pact with an older guy and the story focuses on vampires. In Negima!?, it's a young male who makes pacts with his older female students, there’s only one vampire, and emphasis is put most on the magical incantations. However, each series shares similar elements and has a serious gothic tone; yet at times they can be very cute and even slightly romantic. Not to mention both are VERY funny! In fact, the running gag with the falling pan from -MOON PHASE- occurs a few times in Negima!? read more
They are both by Shaft so have similar styled animation and visual settings. The format is also similar where the protagonists go into dark voids and fights off some sort of evil being in the void and restores the area. One of the only significant differences is that Negima!? has a lot of comically moments as Madoka Magica remains serious all the time.
They both are harem/ magical anime, for one. Also, they both are just brilliant shows. Sure, Negima may center around a magical classroom, but Shuffle expands from the classroom into showing how this magical girls interact with the world. Negima had robots, ninjas, vampires, wizards, ghosts, etc. Shuffle has angels and demons, a kind of step up. So i definately reccomend Shuffle for Negima lovers.