Arc Fatigue: Sid's abandonment issues. While a lot of fans like it given they feel it turns Sid into a much more interesting character that just an average Plucky Comic Relief, some fans also felt the arc was overstaying his welcome given it has being the main focus of his character arc for the first three sequels and wished the writers did something else with the character. Ironically his arc in Collison Course went with the character in another direction and it was universally despised.
Awesome Art: While the first movie had some pretty impressive CGI for 2002, the sequels blow it out of the water.
Diego became less threatening as the films grew Lighter and Softer. In the original movie, he was a fearsome predator who went toe to toe with the leader of his pack. In The Meltdown, he is much less effective due to being given a crippling fear of water. By Dawn of the Dinosaurs, he has become so unfit that his own prey treats him as a complete joke. In this movie however this is a Invoked Trope and he does recover some of his badassery by the end of the movie by defeating a herd of Guanlongs that were targeting Ellie while she was in labour......only for him to fall victim of The Worf Effect in Continental Drift once Captain Gutt and his pirate crew appear and then got Demoted to Extra in the two following movies.
Buck was basically Crazy Is Cool impersonated back in his first appearence in Dawn of the Dinosaurs being able to fight much bigger and dangerous dinosaurs and face any threat in the Lost World easily. Once he returned to the series in Collison Course he didn't do anything as awesome as what he did back in his first appearence besides maybe his introduction scene with him singing Figaro while outwitting the dinobirds to save a egg and spended most of the movie being a glorified exposition-spewer. His appearence in the spin-off has him struggling to face the Ineffectual Sympathetic Villain Orson and ends up being easily captured by him once he gets control of the raptors. To make matters worse, he's saved by Crash andEddie out of all the possible characters.
Peaches is by far the most controversial character of the whole franchise. While the movies were being released many fans considered her the element that ruined the series because of her getting too much focus, switching Manny's characterization from a Heartbroken Badass to a Bumbling Dad and the overall feeling that her subplots and personality were something that fitted more in a sitcom that in a Ice Age movie. As time passed, she gained some defenders who have come to like her thanks to her Character Development that unlike other characters doesn't suffer from Aesop Amnesia and arguably becomes more likable at the same time all the other characters suffer from Flanderization. As such, fans are divided between those who see her as The Scrappy and those who see her as one of the saving graces of the weaker installments.
Sid has a loyal fanbase that regards him as the funniest character of the series besides Scrat, adore him for his role as The Heart for the Herd, cheer for the moments he can stand on his own and think the exploration of the abandonment issues his family gave him makes him a surprisingly compelling character for a Plucky Comic Relief, with that said there's a good portion of the fanbase that can't stand him for constantly playing The Load and Too Dumb to Live a bit too straight (specially in the third and fourth movie) to the point some fans wish Manny and Diego would drop him already so he would stop causing them problems.
Manny is either a compelling Stoic Woobie Protagonist that has very a justificable Freudian Excuse or a Jerkass that constantly treats the people around him besides Ellie poorly and kickstarts the conflicts of the movies out of constantly holding the Jerkass Ball (The third movie and the Christmas Special plot for example were kickstarted by Manny getting pity with Diego and Sid respectively). His characterization from the third movie and onwards only make it a bigger example of this trope by turning him into a Helicopter Parent, with some fans seen it as new ground to explore with the character and others thinking he has become a caricature of his former self and feel his overprotectiveness of Peaches removed most of the things that make him likable in the first place, especially in the fifth movie where he tries to sabotage Peaches's wedding.
Broken Base: There's a division between those fans who enjoy the movies as a whole and those who only find the Scrat scenes enjoyable. Some feel the Scrat sections are really the only worthwhile scenes, as they find the other characters boring, while others think both his scenes and the scenes with the herd are equally enjoyable, even in the sequels.
Cargo Ship: Scrat and his acorn, not helped by the third movie's Scrat subplot basically being a Love Triangle between Scrat, Scratte and the acorn. Also, Buck and his pineapple "wife".
Contested Sequel: The sequels are contested (minus the last two) especially by those who can see past Fox's intentions of trying to create a Cash-Cow Franchise to match DreamWorks Animation's Shrek, especially the third. Some consider it an absolute disaster, others call it the best of the trilogy. Continental Drift is seen as forgivable with some, if only because of Wanda Sykes as Sid's granny and a fun villain. Meltdown is arguably the least contested, with many are off put by its lighter tone while others find it is serious enough and was the movie that continued the story the most naturally.
Many, but notable ones include Sid and Ellie/Sillie and OT3s like Manny/Ellie/Diego. Supreme crack pairings include Peaches x anyone, but these have been mainly only discussed, though Sillie has been written once.
Rudy/Buck is another example, though it also crosses over with Foe Yay Shipping. Sid/Diego probably counts as well, since there is really no viable reason to pair Diego and Sid together, let's be honest, it's Pair the Spares if anything else.
Critic-Proof: All sequels have gotten a rotten rating on Rotten Tomatoes but, until Collision Course, have all done pretty well at the box office.
Ensemble Dark Horse: BUCK. He very well could be the most popular character of the series, due to his Cloudcuckoolander tendencies, very well put together action scenes, having some of the funnier lines of the series, and of course being voiced by Simon Pegg. It's enough that he was brought back for Collision Course (which immediately made some fans interested in seeing the movie solely for him), and him eventually getting his own spin-off.
Manny's first mate and child's names being Millie and Wally, due to one author on fanfiction.net creating a ripple effect with the names.
One bit of fanon is that somehow, in some way, Soto and Shira are related to each other by being either father/daughter or siblings.
Fanon Discontinuity: All of the sequels get this to some degree among different groups of fans, but Collision Course gets the absolute worst of it. Most fans just stop at the third film, which most felt was a sufficient conclusion to the original trilogy and didn't need any more story.
Peaches/Ethan has become this, despite Peaches seeing Ethan as shallow in the fourth film and going off with Louis at the end. Although Peaches/Louis is still pretty popular, even after Peaches married Julian in the fifth film.
Sid/Diego is not an uncommon ship in the fandom and has persisted for quite some time (even with Diego and Sid gaining canon girlfriends) as an Opposites Attract sort of dynamic, built on the foundation of Vitriolic Best Buds from their interactions in the first film.
First Installment Wins: While the sequels have their fans, most will agree that none of them hold a candle to the first movie. As for the sequels themselves, The Meltdown is considered an alright follow-up to the original, but from there, the bases break.
The first four Ice Age films have had decent box office runs in North America, but, at least in the case of the sequels, were overshadowed by the films from Pixar and Dreamworks Animation. Overseas, the series has been very successful, with thefirstfourfilms in the series being the highest grossing animated films worldwide in the years in which they were released.
The movies, especially the first one, gained a lot of popularity in Norway. One reason in particular being famous comedian Dagfinn Lyngbø voicing Sid with his distinct Bergen dialect, who've more than once been recognized as making Sid several times funnier than the original.
The first three movies are very popular on Latin American (with the fourth one being more contested but still popular) and are considered a major Fountain of Memes in a similar vein to Franchise/Shrek and Despicable Me'', like with Norway, part of the reason is that the dub makes a lot of moments funnier.
In 2002, there were no known mammals extinct or extant that closely resembled Scrat. Come late 2011, one was described and named Cronopio. (However, it was not a squirrel, but part of a now-extinct mammal group, the dryolestoids. Furthermore, it lived in the Mesozoic Era, not the Cenozoic as most of the other animals in the films are; the closely related Necrolestes did, but it looked like a mole. Neither could eat acorns anyways.)
This wouldn't be the last time John Leguizamo would play an outcast among his family.note Bit more tenuous a link, but that latter film's setting of Colombia is also known for having once been inhabited by giant ground sloths in the Pleistocene.
Just Here for Godzilla: Several have said that the best parts of the films are the segments featuring Scrat.
Memetic Badass: Scrat is sometimes joked to be the strongest being in the universe, which is somehow supported by all of his feats throught the series (destroying enormous glaciars, stopped the flood from the second movie, came back from the death twice, caused the Continental Drift, created the Solar System and destroyed Atlantis and all life on Mars).
Memetic Loser: With that said, Scrat is also sometimes treated as the synonym of someone with poor luck, to the point the expression "unluckier that the Ice Age squirrel " is rather common in Latin American sites.
Memetic Mutation: Pointing out that random things look like Sid.
Periphery Demographic: Though the films, most notably the sequels, are ostensibly aimed at younger audiences, the movies have attracted a lot of teen and adult fans, who enjoy the original for its depth, humour, dramatic elements, and tearjerking moments. The sequels have admirably brought in teen and adult fans as well, and one reason the movies have such a demographic is because young fans of the original realised that the sequels kept up with the original in some regards (i.e. emotional plots and captivating characters), since some of the teen/adult audience watch the sequels in hopes of seeing characters like Roshan again or just revisiting the herd.
The Scrappy: Crash and Eddie are considered a very bad example of Those Two Guys, and if you remove them from the fourth and fifth films, the story will be entirely the same. They exist only to be hilarious, but their brand of humor, behaving like idiots, gets old after thirty seconds for most people. The Ice Age Adventures of Buck Wild, for some unknown reason, decided to make them the de facto main characters and shunt the main characters people actually like to background extras (or, in Scrat's case, are absent entirely), making the film very tough to sit through for many.
Sequelitis: The majority consensus is that the film series worsens in quality with each film. Each film has a progressively lower rating on Rotten Tomatoes, with the first film ranking at 77% and even getting nominated for the Best Animated Feature Oscar; meanwhile, the last installment, Collision Course ranks at an abysmal 18%. The spin-off, The Ice Age Adventures of Buck Wild, fares just barely better, at 19%, but its audience reaction is still slightly worse (39% vs. 37%).
Signature Song: The ending of "Ellie Remembers" (or in "Goodnight Sweet Possums") from The Meltdown has been adopted as the main theme of the films (it's heard in such poignant moments like Manny confessing his love for Ellie, the birth of Peaches, the end of Dawn of the Dinosaurs and Continental Drift). "Mammoths" has become the secondary theme of the series.
So Okay, It's Average: This is how some critics have felt about all films, even the original to a lesser extent.
Some fans felt that Diego has been wasted in the sequels, as he has a smaller role in the subsequent films than he did in the original. It doesn't help his past as a bad guy is barely mentioned in the sequels outside of a brief talk with Shira about how he left his former pack in Continental Drift and a comment by Sid about how he and his pack tried to eat them in Adventures of Buck Wild.
Four films and nearly twenty years after the first film, we haven't heard so much of a peep about or from Roshan (or any other humans, for that matter.)
Unpopular Popular Character: Sid was abandoned by his own family for how obnoxious they find him to be, all the kids he's supposed to take care of see him as a joke, he's a Casanova Wannabe that no one wants to be around among members of his species (and that's not including the tribe of Mini Sloths that tried to sacrifice him) and the few interactions he has with animals that aren't part of the Herd imply they aren't happy to have him around as well. Only the Herd and his Dinosaur family are fond of him, and even among those groups, he's The Friend Nobody Likes. Among audiences, however, Sid is one of the most popular characters and is seen as the second-funniest character of the series after Scrat.
Many people mistake the glyptodonts for turtles, when they are actually a species of mammal closely related to armadillos. The Ice Age 4: Arctic Games video game even calls them turtles.
Cretaceous and Maelstrom from the second movie; because the two are so heavily stylized it's really hard to nail down what they're supposed to be. Supplementary material identifies them as an ichthyosaur and a pliosaur, respectively, although they look very little like the animals they're supposedly supposed to be. The online game Ice Age Village and official magazine Ice Age: Animal Collection clears up the issue on Cretaceous part by identifying him as Metriorhynchus, a prehistoric crocodilian which he more closely resembles, but not quite.
The Woobie: Scrat has a large amount of sympathizers for how much of a Butt-Monkey he is, albeit not to the degree of Designated Monkey. His antics have led to him being placed in a multitude of life-threatening situations, from being swarmed by piranhas, to falling to the Earth's core, to outright having his body temporarily be turned inside-out. It's telling that when Blue Sky closed down, their final piece of animation was having Scrat finally eat his acorn without any intrusions or misfortunes happening.
" by Rusted Root is a fantastic and bouncy choice for a Travel Montage.