Never thought I'd be the one to break a combo of 5/5s for a Futurama ep, but...
There was just something off about the writing this time. The medical emergencies sequence was funny due to how terribly Zoidberg was handling things (paraphrased, "We still have three perfectly healthy employees!"), but the cartoonish (literally?) nature of the illnesses was off-putting. Futurama has always been slightly bizarre in that way, but there's a difference between Fry getting his arm sliced off then reattached in some pseudo-futuristic way (Lobstertainment), and Leela's bisected upper half hopping around like a bloody pogo stick, or Hermes literally falling apart entirely. Fry's Simpsons-jaundice was funny, but the illnesses got progressively less amusing as they went on. And Bender wetting himself led to what's gotta be one of the most predictable Futurama gags ever, the laughing-then-peeing thing. Who didn't see that coming the moment he said it?
The pacing was shaky as well, with the alternating past/present scenes generally flowing in a somewhat stilted way. I did like the transitions, but I would've liked to see a greater contrast of competent past Zoidberg and incompetent present Zoidberg. That aside, I thought the past setting was rather cool and atmospheric, and a satisfying way for Zoidberg and Farnsworth to meet and bond.
After a shaky start, the second half of the episode got a little back on track. The writing felt less forced and more natural, the conflict was more interesting, and we got to see a cool new side of Zoidberg in his interactions with Mom ("Carol") and Farnsworth. And the climax with the murder device was definitely a lot of fun to watch, even if the double yeti sequence was more strange than anything.
It's such a weird, mixed bag of an episode for me. I quite liked the development of Zoidberg and Farnsworth, but even that was something that I think could've been written more strongly and naturally--their friendship in the flashback never fully solidified for me. In fact, pretty much everything in the episode felt a little less clever than what Futurama's capable of: the yeti twist was unexpected, but altogether not quite a satisfying wrap-up to the decade-spanning plight of Farnsworth, Zoidberg/Farnsworth's reasons for being friends, the whole "he has the disease, oh wait, no he doesn't" thing for Farnsworth, Zoidberg's trade to Mom, etc. Not to mention the sub-par or nonexistent humor, especially for the first act.
I actually do really like the new characterization of Zoidberg. Without a doubt, he was the best thing about the episode and Farnsworth wasn't too far behind, strange plot occurrences notwithstanding. But most everything that went on in the episode not involving their characterization was shaky and a bit lacking from a writing standpoint. 3.5/5 for the mix of good and bad, 3/5 on the poll.