Jim Henson's Creature shop made use of two Skeksi puppets from "The Dark Crystal" to create the Birdlike Halosians in this episode. It was always amazing that you forgot that these characters were puppets, and that is not lost in this episode.
Using the Shield Generator they got from The Zalbinion, Moya's crew fends off an attack from the Skeks- Er, Halosian ship, where Zotoh Zhan had gone to try to negotiate a Truce. But because the Shield was at 60%, it not only protected Moya, but like in the Stargate SG- 1 episode "Holiday" or the Star Trek episode "Turnabout Intruder", the crews minds get switched.
What ensues is one of the best examples of character acting in any unrealized reality.
Claudia Black convinces us, she IS John Criton. Ben Browder channels Rygel, Lani Tupu (Pilot/Bialar Crais) becomes Ka D'Argo, Gigi does Pilot, and Jon Hardy becomes Aeryn. But Claudia wins with the most perfect impression of Criton, especially what a guy might do if ever in a woman's body.
The actors in this series really understood not only their own identities, but each others as well. And that is what makes it stand the test of time. It was believable then, it is now.