The character of "Herbert 'Magic' Williams" (played by Ernie Hudson) is the same character from the original series episode The Leap Home: Part 2 (Vietnam) - April 7, 1970 (1990) (then played by Christopher Kirby).
Original series star Scott Bakula was told he would not return for this sequel, despite lobbying for a continuation to the original series for more than 20 years. Fans even speculated that Ben Song was actually tracking Sam Beckett (Bakula's character) through time to rescue him after the conclusion of the original series, which ended up not being true. Later, in interviews both Bakula and the producers of this show have admitted that the original pilot script for the reboot featured a cameo by Sam Beckett but disclose what his role was. However Bakula backed out and refused to reprise the role as either a supporting or recurring character, without the presence of Dean Stockwell who died in 2021. The producers have since said they have an "open door" policy with Bakula, and that he would be allowed to appear in the show at any time should he change his mind.
Susan Diol played Beth Calavicci both in this continuation and the original A través del tiempo (1989).
This series is a revival/continuation of the original A través del tiempo (1989) TV series. It makes several references to the fact that Dr. Sam Beckett is still trapped in time. It also acknowledges that Admiral Al Calavicci has died, as actor Dean Stockwell had passed away on November 7, 2021.
The premise of the Quantum Leap revival/continuation would have been entirely different if it wasn't for NBC deciding to cancel the original A través del tiempo (1989) at the eleventh hour. They replaced the last scene of the original show that was supposed to set up a sixth season with a simple title card telling viewers that Sam never went home. This was in line with how the original ending was shot but it includes a scene where Al declares he will go rescue Sam. Because of the abrupt cancellation, the studio kept the framework of the originally intended ending; the problem is they didn't think through the implications of this ending, which sees Sam's wife widowed. They didn't even spell Sam's last name right.