These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
Adaptation Displacement: The anime adaptation is sometimes more fondly remembered than the original manga, particularly the more surreal and experimental episodes and films (where director Mamoru Oshii started making a name for himself).
Alternative Character Interpretation: The primary antagonist in the series is actually Lum. She's the one who assumed Ataru wanted to marry her (when all he said was "Now I can get married"), and basically intruded on every aspect of his life since then due to that assumption. Sure, Ataru is a Jerk Ass, but he has a good point about wanting to enjoy the days of his youth and how he's the victim during his rant in the episode, "After You've Gone".
Pretty sure that that was the intended character interpretation.
Big Lipped Alligator Moment: So very many. However, the most notable one occurs in Movie 3: Remember My Love. The orb which contains Lum's curse traps Lum and Ataru within its energies. We then see visions of fairy, dinosaur, and seagull versions of Lum and Ataru meeting and falling in love with one another. Not only does this scene have no bearing on the plot, but it also makes no sense even in the context of Lum and Ataru's predicament. And once it's over, it is never mentioned again.
The idea seems to be that the orb is frantically Reality Bending but just can't stretch it far enough to separate them. A bit rich in light of the rest of the series though. Hell, a bit rich in light of the very next scene.
Thanks to the Reset Button, there are countless Big Lipped Alligator Episodes.
Darker and Edgier: The premise of the 2-parter where Lum's UFO crashes on the Mendou estate, causing her to lose her memory. Shutaro takes advantage of this by claiming her as his fiance and then isolating her from outside contact. When Lum's Stormtroopers get ready to launch a rescue mission, Megane even leaves behind his will as he does not expect to survive, and he's right as the Mendou private army is sent out to kill them!
Germans Love David Hasselhoff: Inverted. The show's focus on Japanese puns and mythology has left it one of the least-known and loved Takahashi properties in North America.
Possibly that, and probably the fact that—unlike every other Takahashi series—Urusei Yatsura didn't get an English dub (aside from a not-too-well-received test dub of the first few episodesnote Movies 1 & 3-6 were dubbed years later by a different studio, and then probably only because they got released in the UK, a market where having a dub is far more vital; Beautiful Dreamer—licensed by CPM—got its own dub which was very poorly done and may have helped kill enthusiasm).
UY missed out on another vital component of popularity—it never got a TV airing in North America, thus there was no way that AnimEigo, a very small independent company, could justify dubbing the show.
On the other hand it remains extremely popular in Italy, consistently remaining the second most popular after Lupin III. Yes, you've read well: in Italy it's more popular than Dragon Ball
Ho Yay: Thanks to a lipstick that draws the lips of the people using it together, Ataru and Mendou end up in a full-frontal smooch by mistake. Both are promptly disgusted: a dappya fish monster even offers the readers three panels to recover from this shock. The participants of the kiss think they require more.
Also, Dracula's bat (a male) disguises himself as a pretty girl to lure Ataru (and Co.) with predictable results. In the end, Ataru manages to plant a big kiss on the bat boy's lips to Lum's ROTFLMAO reaction (she knew it was a male spirit in disguise the whole time).
Les Yay: Ryunosuke goes out with Ran... so she can learn about femininity from a Girly. Ataru actually tries to interfere to try and stop Ran from turning lesbian.
In the anime version of the "magnetic lipstick" story, Ryuunosuke accidentally has a kiss with Shinobu after they get daubed with the lipstick as well.
Nightmare Fuel: "The Horror of Outraged Oyuki." Ran's afraid of her for a very good reason... The BGM especially amps things up.
"And Then There Were None" sends the gang to a desert island (over 20 years before "Deserted Island Syndrome") to be graphically killed off one by one. It was just a prank on Ataru, but still. (Funnily enough, this episode was ranked #2 in the penultimate episode's Top 10 countdown)
Also, the department store marching band in Beautiful Dreamer.
Relationship Sue: Possibly Inaba - arguably, this non-threatening Dogged Nice Guy serves only one purpose in the story: providing Shinobu with a proper Love Interest after she finally gives up on Mendou. Naturally, he comes in very late in the story.