There’s a scene in the first episode where Mork explains that he’s traveling from the 1950s Happy Days to 1978—but that scene did not air until subsequent reruns. The other time travel that I know of is in the penultimate episode where the couple travel via Mork’s ruby red, size eight, time-travel shoes.
Wait! I have one last request! I would like to die with dignity, with honor,. . . and with my penny-loafers on.

Variants

(1)
  1. Mork and Mindy by Anthony W. Marshall and Garry Marshall (14 September 1978).
  2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . written by Anthony W. Marshall