The Devil, or Satan is a character who appears in the form of several characters, including Al, who are depicted in the Season Three episode of Quantum Leap titled "The Boogieman". The part of The Devil / Evil Al is played in that episode by Dean Stockwell.
About The Devil's appearance to Sam[]
When Sam leaps into a fledgling murder/horror/mystery novelist Joshua Ray in Coventry, Maine on Halloween Day, 1964, strange things begin to occur when he and his fiancée Mary Greely, who works as his research assistant, and a teenage assistant Stevie King, visit the old Church "Spook House". The house is believed to be haunted with the spirit of Alice McHorner, the woman who originally owned the house and who in was burned at the stake during the Salem Witch Trials for "tempting evil", The character of Tully reminds Sam of this before saying to him "You know what they say, don't you? Them that dance with The Devil are bound to get scrorched!". Tully then falls off his ladder while repairing an upstairs window after a goat mysteriously appeared and bumped the ladder right from under him. This only compounds things for Sam, who is still trying to figure out why he leaped there.
When Dorothy Jaeger, the town gossip and member of the Presbytrian church, drops dead suddenly of a heart attack in Mary's kitchen, a Black Mamba snake also mysteriously appeared at the time.
Later, it's revealed to Sam and Mary that it was "The Devil", who kept disguising himself in the form of Al to misguide Sam, who was responsible for the deaths of Tully and Dorothy. “Al” appears to Sam by popping up instantly, instead of using the imaging chamber door, and tries to accuse Mary for the deaths. He even quotes the words Tully said about "dancing" with him, although the real Al never heard this before.
Sheriff Ben Masters dies in a car accident just minutes away from Mary's house and Mary herself is rushed to the hospital after having a seizure following Dorothy's death. “Al” appears to Sam when he returns to Mary's house, where it’s revealed that he was really the Devil in disguise.
In a flash of red light, he morphs into an evil version of Al, who had been misleading Sam. Sam instantly recognizes the entity he's dealing with, as he tells the "Evil Al" that he never told him the saying about “dancing with the devil” shared by Tully and cites the fact that he, unlike the real Al, never appeared using the imaging chamber, never walked through doors, and would disappear without using the imaging chamber too.
The real Al appears to give Sam the info he needed on why he leaped and he's also in disbelief as he sees the devil. Sam asks him "Tell me, that this is not real!" as Al says "Yes, he's definitely real!"
The big showdown between good and evil starts. Sam then asks the devil "Why are you doing this?" to which the devil responds "To put an end to your meddling", explaining that Sam had been putting right what the devil had put wrong. When Sam says that he's trying to get back home, the Devil grabs him by the throat, saying "Well, you're not going to make it!" as the two spin around the room. Sam is flung to the floor and then awakes back at Old Spook House at the beginning of his leap into 1964. Tully, still working on the upstairs window, is now clinging on the edge of the window sill. The real Al appears and tells Sam that he's there to save Tully from the fall, which he does.
Possible connection to "The Evil Leaper" Project[]
As the devil manifests himself in morphing into the form of various characters in "The Boogeyman" episode, most notably Al, a bright red flash appears, similar to the light which appears when the "The Evil Leapers" use their form of Ziggy, Lothos, in their malevolent leaps into various people, to do exactly the opposite of what Sam and others in Project Quantum Leap aim to do, to "set things right that once went wrong", or, in the case of the Evil Leapers, "to make wrong what was once right", which causes us to question the power or entity which fuels their leaps are simply by their input into Lothos, or are they, unlike Quantum Leap, which is believed to be "God" inspired, are inspired by Satan???