The Leap Back - June 15, 1945 - S4-E1
Plot hole: Sam is trapped inside the imaging chamber without a hand-link for the first half of this episode. Yet, somehow, he is still able to follow Al around town. The chamber is only so big. Without the hand-link to recenter himself on Al once he's traveled beyond the walls of the chamber, Sam would have been unable to move much further than the town square he appeared in.
Play Ball - August 6, 1961 - S4-E2
Continuity mistake: The mud stain Sam gets in his slide covers most of the front of his baseball jersey. But a few shots later, it becomes a much smaller streak on just the left side. (00:06:30)
Continuity mistake: In the scene in the courtroom, when Kevin is being questioned by the prosecutor, she introduces several photos of Katie to the judge. The judge keeps two or three of them, and the prosecutor carries one to the witness stand. As she is carrying it to the stand, it can be seen that it is a photo of Katie wearing a dark top, with what appears to be a fluorescent light over Katie's head. The prosecutor then places the photo on the stand for Kevin to view, and it shows Katie wearing a white hospital gown with blue dots. After the prosecutor questions Kevin, the defense attorney walks over to the stand and picks up the photo. This time, it shows Katie in a red v-neck top, with no light above Katie's head. (00:30:35)
The Wrong Stuff - January 24, 1961 - S4-E7
Factual error: Al says he was an astronaut and flew around the moon, describing a mission that sounds precisely like Apollo 8 (10 orbits around the moon, reading of Genesis, etc). In the season 2 finale episode 'MIA, ' set in 1969, Al says he was shot down in Vietnam two years earlier, in 1967, taken prisoner and not freed until 1973. The Apollo 8 mission flew in Dec. 1968, meaning Al would have been a POW at the time. Also, NASA astronauts aren't generally sent to serve as pilots in active war zones.
Dreams - February 28, 1979 - S4-E8
Character mistake: When Sam is trying to explain to Al how he feels the person he's leapt into, Jack, is still in his head, Sam asks Al if he remembers how their personalities got mixed up when they simul-leaped. Al says he does not. Three episodes previously, in Permanent Wave, Al asks Sam if there's still some of him, Al, left in Sam because of the way Sam is behaving toward the twins. So Al remembers in one episode, but in another, later episode his brain is somehow still swiss-cheesed from the leap on this particular detail. (02:33:40)
Running For Honor - June 11, 1964 - S4-E12
Character mistake: When Sam first sees his reflection in the locker room mirror, his counterpart comes into the scene just a tad too late, making the reflection not match.
A Song for the Soul - April 7, 1963 - S4-E15
Revealing mistake: When Al jumps into the shot out of nowhere on the steps after the record producer leaves, Sam and the two girls abruptly move, giving away the technique to achieve Al showing up. The transition is usually smoother, this one happens to be rough and noticeable.
It's A Wonderful Leap - May 10, 1958 - S4-E18
Continuity mistake: When Sam goes in to talk with Max's father, Sam/Max is wearing glasses. But in one brief shot, his reflection in the mirror isn't. (00:20:05)
The Curse of Ptah-Hotep - March 2, 1957 - S4-E20
Continuity mistake: When he starts swinging the pick-ax, Sam's bandanna instantly moves between shots from around his neck to over his face. (00:19:25)
The Curse of Ptah-Hotep - March 2, 1957 - S4-E20
Continuity mistake: The size and shape of the hole Sam creates, when he breaks through the wall, is considerably different on the outside than it is on the inside of the burial chamber. (00:20:10)
Chosen answer: Per the Quantum leap page at http://www.scifi.com/quantum/episodes/season5.html. 8 August 1953: An enigmatic leap lands Sam in a Pennsylvania tavern, as his own grown self on the day of his birth. As Al and Gushie work frantically to locate him, Sam befriends a wise bartender (popular character actor McGill, who'd appeared in a different role in the very first "leap") and a group of coal miners. As a host of familiar-looking faces pass through the bar - with different identities than Sam remembers - Sam ponders his life of leaping with Al the bartender, who tells Sam he controls his own destiny. Pressed for more, Al the bartender simply shrugs and says, "Sometimes, 'that's the way it is' is the best explanation." Sam realizes he must right at least one more wrong before he can go home, and leaps back to tell Al Calvavicci's wife Beth (from "M.I.A.") to wait for Al, who will survive Vietnam and come home to her. The closing title cards state that Beth and Al have four daughters and will shortly celebrate their 39th wedding anniversary ... and that Sam Beckett never returned home.
Boobra