Psycho Jenny(or Genie) is a Demon from Devilman who has mindwiping powers. She appears as a big head with long hair and arms/legs. She is also loyal to Satan.
In here she is the one who brainwashed Satan into thinking s/he was Ryo Asuka to infiltrate the human world. She later stopped Akira Fudo from fighting demons for a time during the demon invasion and it is later revealed thet she sent mental images of the demons past into the Demon Mask for Ryo/Akira to see back in the first OVA/manga volume, since the mask was fake and did nothing without Psycho Jenny).
CB Chara Go Nagai World
In here, she appears in front of Ryo Asuka and informs him that he put Amon's soul into Kaim and that she finds Ryo's Satan form prettier than his Ryo form. Ryo comments that Psycho Jenny looks the same in chibi as in her regular form ,a comment which she doesn't mind and kinda likes. In the 3rd OVA, she tells Sirene and Kaim to be happy as per Satan's orders and at the end, teleports Miki Makimura to the Violence Jack world and asks Jack where Satan is.