Devilman

Devilman is a franchise created by Go Nagai as well as one of Dynamic Productions' most famous series next to Mazinger. Nagai created the franchise when asked to make a downplayed version of Demon Lord Dante for an anime. Shortly after the anime was produced, Nagai released a manga version that told a separate storyline. The franchise amassed several spin-offs including Devilman G, Amon: The Darkside of the Devilman, and Devilman Lady.

Summary
Devilman tells the story of Akira Fudo and his fight against the demons that have been appearing throughout Japan as the titular Devilman.

Depending on the media, the series goes through different turns of events. In the anime the original Akira Fudo was killed and Devilman was once an elite guard of Zennon who took Akira's form until deciding to protect humanity after falling in love with Akira's childhood friend Miki Makimura. In the manga version, Akira's friend Ryo Asuka (later revealed to be the fallen angel Satan) has Akira bonded to the exceptionally powerful demon Amon. Keeping his humanity due to his pure heart, Akira fights the demons alongside Ryo until Ryo regains his memories as Satan.

Devilman in Mazinger
Characters from the Devilman franchise have occasionally appeared as reference or directly involved in the Mazinger series. Sirene is seen in most of these references.
 * In the original Mazinger Z manga, a statue of the anime version of Devilman is seen as a decoration for a bath.
 * Mazinger Z vs. Devilman is a crossover film that involves Akira meeting Koji Kabuto as Dr. Hell teams up with Sirene. It also debuted the Jet Scrander on animated media before its actual appearance on TV.
 * In MazinSaga, Akira Fudo appears as the grandson of God Kaiser Hell and wears a suit that acts as a counterpart to Z based on Devilman, Devilman X.
 * The use of demons are also used including Psycho Jenny.
 * In Mazinger Angels, Minerva X's alternate flying form is based on Sirene.
 * A statue based on the manga version of Devilman appears in the hot spring chapter.
 * Akira and Miki appear as students in the same school as Sayaka and in a mini-arc Akira as Devilman assists the Mazinger Angels team when Dr. Hell awakens the Demon tribe from the Himalayas. Here Akira is based on his anime counterpart rather than the manga.
 * Mazinger Otome featured Devilman as distorted image of Koji Magami due to Grace D. Fleed's poor vision at a hot spring.
 * Mazinger Otome Taisen featured Majeeg's second form as a resemblance to the fused body of Sirene and Kaim.
 * Mazinkaiser SKL features a mecha called the Wingle which was adapted from Minerva X's Sirene mode and made into a form resembling Devilman Lady, the main character of the manga and anime of the same name.
 * Mazinkaiser SKL Versus features several mecha based on demons from the Devilman franchise.
 * Akira and Miki make short cameos in the OVA's third episode.
 * A spin-off manga by Team Moon, Devilman vs Hades is about Devilman wandering through the underworld encountering old foes and eventually the Emperor of Darkness.
 * The mechanical beasts Glory R2 and Devila X1 both share a striking resemblance to Devilman.
 * In CB Chara Go Nagai World Akira Fudo is the main character, however Koji Kabuto, Sayaka Yumi, Gamia Q, Count Brocken, Dr Hell, Baron Ashura, Garada K7 and the Gool all appear in it as well.
 * In the first episode of Shin Mazinger Shogeki! Z Hen, Masa Bokuto is seen working for the Kurogane house, firing his hunting rifle at a group of Iron Masks.
 * The Warrior Beast Iguanas seems to be partially inspired by Devilman's Lacock.