Total Recommendations: 34
Perverted humor exposed wide open and without any care. Most of the characters in both are rather experienced in, uh, this sort of humor. Sexual humor is always present in both anime. Also, both anime run on whether or not you like that sort of humor.
Both anime are part of the recent huuuuge moe wave that's coming on. Both are focused on a particular interest, and both anime actually show the interest. Both anime have an all-girls cast, and even their personalities are similar. Ritsu and Kotone are both the super-energetic person, Tsumugi and Elizabeth are both the adorable, soft-voiced but rich girls and Yayoi and Azusa are the overly cute/moe girls. Both contain suggestive lesbian content and their demography is mostly male.
Both anime has a dark atmosphere with tons of cussing and good gunfights. Their episodes are episodic; each and every episode telling a different story. Both anime are about hunters trying to get bounties in order to get more money. Both anime has an (almost) useless character (Cowboy Bebop - Edward, Black Lagoon - Rock) as well as a charming but badass + crude-mouthed girl that fights pretty well. (Black Lagoon - Revy, Cowboy Bebop - Faye) Plus, gunfights!
Both are about tennis, and a group aiming for the nationals. Warning: Softenni has MUCH MUCH more comedy than Prince of Tennis.
Same type of humor that uses 'rape as comedy' device often. Both are about 12 minute episode lengths and have extremely crude humor. The strange art style is similar as well.
Both have the 'boy gets into a completely different world' plot, the boy sucked into the world of the non-human lead. Both are fantasy genres that are fairly recent. (Heck, they're even both 2011 spring titles)
Both female leads are tsunderes. The female and male leads in both of these anime have the same seiyuus. Basically, Hidan no Aria (Aria the Scarlet Ammo) is Toradora with guns.
Clannad's Fuko (first) arc reminds me of AnoHana. Meiko and Fuko's personalities are very similar and they start being forgotten, one by one. However, the male lead tries his best to remember the female lead with the help of his friends. Both are extreme tearjerkers.
Both male leads defeat youkais, and said male lead isn't human, along with a lot of the other cast. One of the female leads are humans and is involved with the male lead. The male lead is extremely overpowered, but rather stupid. The said male lead is involved in a demon patrol, but that male lead is the only one who can actually fight. There is a person who uses ice to defeat youkai in both anime.
Both anime focus more on a club that does odd jobs, and their episodes contain the odd jobs.
Both anime are about overcoming odd fears as well as taking place mostly in a club setting. The male lead is forced into the club. Both animes' episodes are episodic, until the end.
Both anime are about samurai girls with an ecchi action feeling. Both anime have a bit of Japanese history in it. (Samurai Girls - Tokugawa shogunate, Sengoku Otome - actual time-traveling, Nobunaga shogunate) Both anime have an all-female cast. The lead's world turns upside down as the story really takes place.
Both anime have 'cute girls doing cute things' with merely implied yuri scenes. Both are slice of life anime with the same type of comedy, mostly random humor. The characters are extremely similar with all-female cast. Both follow the regular days of students, its setting being in school.
Both are fantasy titles that involves magic. The protagonist is shoved into the politics of the setting. Both protagonists happen to be already good in what they're doing in the start of the series, but fit in the 'bumbling idiots' section.
Both are anime with rather beautiful art with slice of life in it. Most of the cast are females, and all of the characters have very different qualities in comparison to each other. An event that actually starts the story changes the protagonist forever.
Both are moe, cute anime that are in the slice of life genre. The art style has the same feel to them, but not quite the same. Both focus on interests and hobbies as well as day-to-day life.
The male lead is VERY similar, and he gets dragged by the female lead on her many adventures. The two anime are both about clubs, as well as some side-stories.
Action with pantsu. Also have weak characters. WARNING: High School of the Dead has zombies and more gore.
Typical characters from their genres (and in general) fighting strange demons from another world. Not bad but not good supernatural/action/super power anime. One of the female protagonists do not know how to fight and the main male protagonist wants to protect that female protagonist that don't know how to fight. Main male protagonist was your typical, usual teenage boy until the present. (present=until the anime starts or until a few episodes)
Same type of crude humor and similar styles. Also very fast-paced. Short episodes that'll made you lol. The main characters try to be rough and tough, which they really aren't.
Both are moe anime that are funny. Both characters are really cute and the characters have a wide variety of personalities, from the crazy/insane Ritsu/Mitsuba, to the silent/moe Mio/Hitoha. There are other teachers involved in the craziness, especially Yabe/Sawako. BEWARE: Mitsudomoe is MUCH, MUCH stranger than K-ON.
They both use monsters to fight other monsters and humans take care of them. Both are kids' shows filled with drama, action and more. Those monsters become stronger, and, as they become stronger, they can turn into more powerful beasts. There's a lot of monsters in the world, but the main characters only choose a few monsters to capture.
Both are dark anime that makes fun of social problems. Both makes references to other anime. The protagonist is introduced to a happy, cheerful person to try to cure their problems but the protagonist denies her help.
Dark humored anime aimed at a more mature audience. A lot of people die here, even the main characters, but they can be revived. They have a pretty simple plot, and they both parody genres. There are other people in the organization/other angels involved with the killing/randomness.
Same type of humor (brutal, physical humor), has beautiful/loli-like women... who can destroy you. Both are good at destroying other people and both parodies the magical girl genre with a ton of violence.
Black sense of humor, evil blond female leads, destruction, chaos.
Funny anime, some leads have sci-fi-like powers. Male lead is dragged onto female lead's world. Normal male lead develops a relationship with a female lead with supernatural powers.
Psychological, intelligent, smart leads. The leads are anti-heroes while the antagonists are heroic villains (or whatever you call a villain that's acts good). Both leads want to change the world and manipulates other people. The person who gives the power follows the current user. The anime makes you predict what's going to happen, and something unexpected happens (except for VERY few cases). The user also goes insane because of overusing their given power.
Both are like a chess game. Light and Lelouch have a magical power (Light - Death Note, Lelouch - Geass) and they both want to change the world; Light freeing the world of criminals, Lelouch wanting Area 11 to become Japan again. They both take on aliases to cover themselves (Lelouch - Zero, Light - Kira, but Light just accepts the alias). The two protagonists act more like an antagonist. Suzaku, Lelouch's rival, is more of a protagonist, and same goes for Lawliet, Light's rival. After Light and Lelouch gets the power, the people who gave him the power follows. There are also other users of the power the character has. So, basically, Code Geass is Death Note, but with mechas (Knightmares).
They have a simple plot and they are really random. They focus on high school girls and their teachers; even the lead characters are similar. (Kagami - Mio Konata - Ritsu Tsukasa - Yui Miyuki - Tsumugi)
They're both magical girls anime, though Ojamajo is more for a younger audience.
Anime/manga references hidden (or popping out in your face) in each episode, but SZS has a more darker art style. Most of their characters are females, and they're both funny. Both series also center their plot around high school students, including teachers and other side characters. Oh, and Sayonara Zetsubou Sensei sometimes add a little dark comedy in the mix.
Haruhi and Konata has the same seiyuus, both have random comical scenes, both are random, and Itsuki and Daisuke (Daisuke comes in Lucky Star episode 20) has the same seiyuus too.