Johnny Novgorod said:
The Office S06E14, "The Banker"
It's just a clip show. The title banker visits Dunder Mifflin to debrief Toby from HR about the company's antics (cue the clips). He calls himself "just a glorified fact checker" during a brief talking head before pausing and correcting himself: "I'm just a fact checker". Same applies to the episode. You might call it a glorified clip show but really it's just a clip show.
Cowboy Bebop S01E21, "Boogie Woogie Feng Shui"
The weakest episode in the whole show. The series alternates between developing character-centric episodes and the more lighthearted bounty-of-the-week episodes. This one is meant to be centered on Jet Black, except the character has more or less cashed out by now, having gotten over his personal femme fatale and tied every loose end surrounding his past-defining trauma. This episode is supposedly about his relationship with a girl (daughter of an old friend) but the show can't decide whether she's a romantic interest or a surrogate daughter, so it doesn't take it anywhere in the end. And the scavenging hunt plot just isn't very interesting (or even comprehensible).
Samurai Champloo S01E12, "The Disorder Diaries"
Another clip show episode. I guess I could cite every clip show ever made, including the infamous Seinfeld finale, and that one episode of Evangelion, but the reason this one came to mind is that it always seemed like too soon in the series for a clip show. There just isn't a whole lot to recap.
The Bebop episode was fine for me. I didn't mind a lighthearted Jet episode. I've seen that episode multiples times, and it was pretty clear they where having a father/daughter relation. I'll watch it again to double check, but I never saw that one as the weakest.
The Samurai Champloo episode you are dead on correct. A lot of anime from the 80s, 90s, and early 2000s suffered from this. Especially the anime that was 25-26 episodes. Hey, creators & writers, stop wasting our time on shit we already know. If you can't think of anything to do with your characters, don't bother and stick with an episode or two less. Luckily, this trend has mostly died in anime now, but was a huge ***** for short or long running anime. Kill La Kill even made fun of this trend.
Powerpuff Girls (98)- "Moral Decay", "Monkey See, Doggy Two", and the one where Bubbles gets glasess. Two episodes consist of characters being derailed and a lazy retread of the Mane Event and the episode where Mojo first appears. I hated Moral Decay so much. Mime for Change too for its shitty and unnecessary ending. You can blame the CN exes for that last one.
Avatar: TLAB - Avatar Day. Nothing happens, nothing is learned, and villagers are petty assholes. They want to kill Aang for pettier reasons than the fucking Fire Nation! For something Avatar Kyoshi was justified in doing. Why couldn't the fire nation come and kill these assholes after the Gaang left. I would have the most devilish smile on my face.
Foster Home for Imaginary Friends. Debatable as everyone became an asshole after season 2. But "Everybody Hates Bendy" is the worst episode ever, and why Lauren Faust ever made an episode like this beyond me. The villain never gets properly punished, and is one of the worst karma houdinis in animation history. Never has an episode title been more accurate.
Hey Arnold - Iggy. Do I need to say anything? .....Bunny Pajamas. This is an episode so bad, Nick & the creator of the show hate and regret it. The only way to see the episode is on DVD or online. They refuse to air reruns of that episode. I also hated the Longest Monday & most episodes that focused on Helga. The early season really suffered from this.