Another season 4 fan here. Having rewatched the series recently, season four is overall a step down from season three, and has some mediocre-to-abysmal episodes ("A Perfect Murder", anyone?); some of it feels a trifle of a retread (Scorpius to Grayza as Crais to Scorpius) but also features some excellent hours of Farscape.
The whole return-to-Earth arc and the TV special about is greatness, "Don Quixote" was fun... and the We're So Screwed concluding arc is every bit as good as the arcs in earlier seasons. Some of Crichton's best speeches are there, and this line stuck with me on this rewatching time around:
"I want wake up like an emperor."
You can tell in The Peacekeeper Wars. I'm not sure if Lani Tupu wasn't quite able to do the voice after being away, or if they didn't modulate it correctly, but it sounds off in the miniseries, and much closer to Crais' voice.
If memory serves, they basically had a new guy doing the sound and he didn't know how the old guy did the Pilot modulation.
Now this will blow your mind: Jonathan Hardy, AKA Rygel, appeared onscreen in the series as a creator of the Leviathans during the "Kiss the Princess" arc.
Alright, since that's basically his voice on both characters it most absolutely will
not blow your mind, but hush.