Key the Metal Idol

These two titles share psychological themes, ideas about reality, existence, soul, identity and humanity and its' connection to modern society and technology. Looks like Key is the predecessor to all anime that raise spiritual queries. 

What should one expect of an android seeking to become a top pop idol. Why, one should expect a character learning what it means to be human so that soul will end up in their idol work, but both of these series touch upon the humor of this. 

These two titles share not only some psychological themes (identity complex, definition of humanity, communication and relationships, courage/fear, self-realization/suppression etc.), but I also find the art style quite similar. I can even find some resemblance of characters, where as Key alias Tokiko Mima shares the same behavioral archetype as Rei and Sakura Kuriyagawa reminds me of Misato. 

Both about robots trying to fight enemies who are much bigger than them 

Both are soft cyberpunk stories about android idols in search of their emotions. While the plot events and MC's impact on the world differ, there are multiple shared elements: a conspiracy, action parts, the character development of the female idol MC from stunted to emotional, and of course the finale in the form of a song performance. Key is a diamond in the rough whereas Vivy is a highly polished modern anime. But if one can cope with 90s animation and 4:3, it's worth learning about the roots. I haven't a shadow of doubt about the direct influence of Key on Vivy. 

Both are about artificial idols controlled by humans. They portray Idols in a negative, critic way. Both anime (in particular key the metal idol)have psychological aspects and a cyberpunkish, sad and dark atmosphere. 

Features a naive robot girl as a lead character. Chobits is more of a romance story, but I found myself drawing a lot of parallels between Chii and Key, even down to their voice. Am I the only one? 

While the plots are not at all similar, the aspect of the main character's search for her history and acceptance by others is a strong theme. Also, there is a strong sense of "sisterhood' between the main character and the supporting character, mysterious supporting characters whose intentions are not immediately clear, and a few plot twists along the way. Where Key lacks action, Kurau provides plenty of it, and the fact that Key is set in the present day contrasts with Kurau's futuristic world. 

Another two titles that share similar psychological themes, ideas about reality, existence, soul, identity and humanity and its' connection to modern society relationships and technology. Looks like Key is the predecessor to all anime that raise spiritual queries. Oh, and you can see how some scenes from Key (for example the doll creating scenes in the OP) were used in GitS too. 

Now it's no surprise that the similarities are due to that they are from the same studio, just decades apart. While Key the Metal Idol is present day Akudama Drive is full cyberpunk. However both have similar themes with robots and "evil organizations". I'm homing to see more original anime like these in the future.