Overman King Gainer

Both are made by Yoshiyuki Tomino and feel like 1980s anime even though they were made in the 2000s. They both have young genius pilot protagonists joining a small group opposing a nation simply because they were at the wrong place at the right time. Both anime also contain some nonsensical plot points which progress the story forward. 

Wacky, Wild, Biopunk, futuristic, and mecha. Definitely similar. 

This again seems a weird recommendation, but there is logic. The shows have a similar sense of gently absurd humour and a social message, as well as some character parallels which are pleasantly amusing. 

I'm fairly certain King Gainer was influenced by Jojo, or at least is influenced by the type of Manga that it stems from. King Gainer has that flavor of procedural battles, that are all oriented around strange gimmick powers that the characters have, how those gimmicks bounce off of various elements like the environment, or the personalities of the fighters, or how each gimmick stacks or counters other gimmicks. The characters also have that unhingedness that's required for a work like this. Ookouchi Ichirou (Code Geass, most famously) is also serving as writer on this series, so you'll get that kind of bombastic-ness. Pointing out all of these similarities to Jojo is strange to say though, considering that the director/creator of King Gainer is Tomino Yoshiyuki, who's been working in anime for longer than Jojo's even existed. As far as anime is concerned, Tomino is as old as they come. You might think of Jojo as a classic manga, older than dirt, but Tomino likely sees Jojo as a hot trend (in 2002) to try to take advantage of. It's like Tomino's the old guard, looking at Jojo and the manga like it, and trying to replicate it and modify it with his classical style, while retaining the appeal. The Jojo TV anime was a bit a letdown for me because of how un-adapted all of the fights were. It's composed of lots of stills that very directly display a beat-by-beat replica of the manga, with no room to have fun. Anime is ultimately a different medium than manga, and while the imagery can broadly be translatable, and I certainly am not a sakuga-freak that thinks everything needs to move all the time, the excitement of Jojo's manga was pretty badly deflated for me by this adaptation. Every shot in Jojo lingers for a second too long, just to make sure that you never miss any piece of visual information. It just reeks of manga adaptation, rather than feeling like a composed, flowing, video work. If you don't know what I mean and need a really direct example, rather than King Gainer, I'd recommend the Jojo OVA, which is really well-directed. This is what I mean by saying King Gainer feels more "classical". There's no source material, and even if there was, Tomino is not the kind of director to just lie down and directly adapt material. There's lots of interesting direction, a great sense of cinematic flow, rather than the boxed-in feel of the Jojo tv anime. Did you know that the famous cubes you see in action scenes these days are actually from this show? I'm not kidding, they're called "yutapon cubes", and this is the very first time that animator starting using them. This is the kind of show where a unique animator-based expression can crop up. This is what I mean when I say Tomino's directing is good. However, this is a recommendation with a lot of asterisks. If you don't like Jojo *that much, and get kind of annoyed with it when it's indulging too heavily in what it is, and wish it progressed more, or wasn't so monotonous, or had deeper characters, then King Gainer isn't going to be the answer to all your problems, but if you're curious about a show with a similar general vibe, I think I'd recommend it. Koyasu Takehito who plays Dio in Jojo, is also in King Gainer, playing a character that's pretty similar to Dio. It makes me wonder if he was type-cast as Dio because of this show. Then again, he may have just been type-cast based off of Zechs, from Gundam Wing, but then that would just mean he was being type-cast as machiavellian blondes, which is an archetype Tomino cemented anyway. Does that make Dio a Char-clone? read more 

Both are post-apocalyptic mecha series with teenage leads who get swept into adventuring across the wastelands left on earth. Despite their dismal settings, both shows manage to maintain a positive and lighthearted atmosphere with their endearing casts of characters. 

From the socially awkward and mildly irritating protagonists to the enigmatic girl with strange hair, these shows appear kinda similar. In terms of tone, both are gently comedic, mostly relying on the interactions between teenagers and authority figures with a background of war. 

Pilots fighting outside of the box in battles instead of just using beam weaponry and machine guns. Both have very original and obscure mecha designs. Both have a relatable main protagonist, a geeky gamer instead of a sporty tomboyish girl. 

Wacky, nonsensical, Tomino-directed giant robot shows with great action scenes. Daitarn 3 is old and a bit ugly, but like any good Plain Jane, it more than makes up for being unattractive by having great character(s) and charm. 

Both are mecha shows by Tomino that offer a silly, happy-go-lucky take on a genre often crowded by more somber titles.  

Both are made by "Happy" Tomino, and have similar plots, characters and robots (Even on the way they fight!). 

Gaming nerd boy gets stuck in something bigger, where his gaming skills come in handy.