Mork in Love - S1-E5
Continuity mistake: In the scene where Mindy shows Mork the differences between herself and the mannequin Dolly, Dolly is in a different position in every shot. Her legs are sticking straight out when she first 'sits' down, then bent down, then straight out again, then closer together and the left shoe is on backwards, then her right shoe is backwards, then she's tilted to the left and finally she's sitting straight up.
Answer: Maybe s02e02, "Mork in Wonderland, Part 2"? Mork started shrinking in part 1 and continued till he became microscopic and fell down a space warp into the lake of another world.
Bishop73
Yes, that was it. I found it shortly after submitting the question, but thank you anyway.