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.
Base Breaker: The Chipettes, actually. People who originally grew up with the 1980s series are pretty much used to them, though people who originally grew up with the original Chipmunks from 1958 through The Alvin Show and even up to 'A Chipmunk Christmas, however, aren't so fond of them.
Dave Seville, to a lesser extent. He's either a kind hearted man who loves his family but gives them tough love or an annoying father who treats them like garbage. The above parody (See Alternate Character Interpretation) hasn't helped this.
Foamy could be considered an angry, opinionated, underground version of Alvin.
Crowning Music of Awesome: While some of the songs The Chipmunks cover are really good, nothing beats the great soundtrack of The Chipmunk Adventure. It helps greatly that most of the music is original work for once.
The songs from Alvin and the Chipmunks Meet the Wolfman and the opening number for Alvin and the Chipmunks Meet Frankenstein.
The Chipmunks' covers in all three movies. Every. Single. Song.
Many people even consider the covers better than the original songs. Most YouTube videos of them will have people stating that or how their cover of it made people like the original song in the comments.
Face of the Band: Subverted. While Alvin gets a lot of attention, is the lead vocals on almost every song they have, is the star of the show, and was #44 on TV Guide's list of top 50 best cartoon characters of all time, Simon and Theodore are anything but forgotten or put in the background. Each of them have their special and memorable moments in the spotlight, each have their own fanbases, and all three of them share balanced screen time. Change anything, and it would not be the same.
Fan Dumb: Some people have to be convinced that Alvin and Brittany are the oldest of their litters, and Simon and Jeanette are the middle children. Although has been distinctly mentioned a few times in the 80s series, the misconception can be somewhat justified, not just because Simon and Jeanette are taller than Alvin and Brittany, but because they're also smarter, wiser, and more mature (with age comes wisdom).
Fan Nickname: The term "to chipmunk a song" means to edit the song to give the vocals (and consequently the rest of the song) a higher pitch. The term finds its roots in these characters. Just add "chipmunk" to any search for a song on YouTube, and you're bound to find one.
Oh, and watch out for fake chipmunked songs. "Real" chipmunked songs are actually pitch-adjusted (like real Chipmunks songs) and are the same length as the original. The fakes are the result of simply speeding up the original and are much shorter. Some people think that the former sounds better than the latter.
Fan Community Nickname: Some fans call themselves, "Chipaholics", though there really isn't (so far) an actual community nickname for the fandom.
Crack Pairing / Broken Base: There is a serious divide among the fandom with canon shippers and mixed shippers, it occasionally even grows to a point where the two groups of shippers practically go to war over why their respective shipping is better, and why the opposing shipping sucks.
Speaking of phases, the crack pairings go through many different phases among the fandom, which almost always ensures a string of fluff fanfics from different authors. Popular phases over the years have included pairing Alvin with Eleanor, Simon with Brittany, Dave with Vinny, and even Alvin with Simon, however, none of them have quite put the "crack" in "crack pairing" as much as Dave and Brittany, with even a few fanfics involving Dave impregnanting Brittany.
Moe: Eleanor might qualify. It helps that she's Theodore's counterpart.
Jeanette definitely qualifies. Take a look at the fandom, fans quite often put her on a pedestal.
Moral Event Horizon: Mrs. Grudge in the ’80s cartoon gets one in the Chipettes backstory: Binding, gagging, and locking the Chipettes away so Olivia wouldn't take them away with her new parents and she'd be able to make money off the three girls. They managed to escape, though.
In the second movie, Ian crosses it when he threatens to barbecue the Chipettes if they don't do what he says. After doing this, it's almost difficult to accept the Enemy Mine situation with him in the next movie.
Love It or Hate It: This has increased among much of the Chipmunk fandom in recent years. A large majority of the fan base grew up with this particular series and love it, especially for nostalgia. On the other hand, some fans hate for one of either two reasons, because it focused less on the music (unlike The Alvin Show), or they're sick of Bagdasarian Productions releasing the same handful of episodes on DVD over and over again.
Seasonal Rot: During the DiC era of the series, the stories, as well as the overall production, slowly, yet steadily, grew weaker and weaker, compared to the quality of the earlier, Ruby-Spears era.
The first movie didn't do very well with the critics in the first place, but at least some of them liked it. The reaction was the same for the sequel. But by the time the third one came out, it became almost unanimous that the series had outstayed its welcome.
To clarify, the third movie did horribly with the critics but was among the highest-grossing films at the time. The critics were quick to make insinuations on what kind of person would actually like such a movie, as reflected in the Rotten Tomatoes consensus: "Lazy, rote and grating, Chipwrecked is the Lowest Common Denominator family entertainment that is strictly for the very, very, very young at heart."
Tainted by the Preview:. Some fans who grew up on the 80's cartoon did not gravitate towards the eponymous Chipmunks looking more chipmunk than humanoid, and fans in general were not amused by the poop-eating gag shown in the trailer. Much to the latter's relief, the movie only really had two instances of toilet-humor.
Sequelitis: Mostly averted with The Squeakquel but may or may not have happened with Chipwrecked, which received mostly negative reviews and even David Cross went on the record of saying that just the making of the movie was the most unpleasant experience he'd ever had.
Actually, what Cross meant by that was that the directors made him wear a hot, stuffy pelican suit on a cruise ship for a week instead of using a double (because for the first half of the movie, you can't see who is inside it). He didn't mean the whole movie itself.
Squick: In the second movie, Alvin flirts with some human girls. High school girls. Think about it, then take a long shower.
Simon eating poop.
At least he didn't swallow it. Double squick.
The Chipettes having more feminine bodies in the movies. In the show they were in Elementary School!
Their first appearance has them naked. The dance scene that follows is kinda creepy.
The Chipmunks attempting to cover up what's happened to Dave's aunt by stating she's taken up pole-dancing.
We're Still Relevant, Dammit: The Squeakquel, which saw the Chipmunks attending high school (and behaving as such), singing mostly modern pop tunes, and spouting lines from such films as "Silence Of The Lambs" It ultimately wound up crossing over with...
What the Hell, Casting Agency?: Some felt this way about Justin Long getting cast as the voice of Alvin, since the inevitable voice modulation would make his voice unrecognizable.
Just Justin? What about all the chipmunks?
Doubles as Executive Meddling, as Ross Bagdasarian, Jr. and Janice Karman were originally going to voice the Chipmunks (just like in the cartoons) but the studio insisted celebrity actors do the rolls. At least the original duo provide the singing voices. In fact, only Simon has a new singing voice compared to the cartoons.