Thomas Clarke’s review published on Letterboxd :
The issue with sequels is, how do film makers keep the ideas and concepts of the original movie yet allow them to evolve and develop in a way that not only adds to the formula and finished article, but does so in such a way that it keeps in touch with what the original had set out to achieve. This issue is made worse when films run for multiple sequels, leading to a majority turning up poor or disappointing, especially if the original is held in such high esteem. Making a good sequel is hard, but when it is done correctly it will bring more delight to those who are fans of the series. This is the case with Ice Age 4. After the slight disappointment that was Ice Age 3 - Dawn of the Dinosaurs, Ice Age 4 has reverted back to the glory days of Ice Age 1 and 2.
The jokes come thick and fast in this installment, and the film offers enough for young viewers to find constant enjoyment, and enough content to keep older fans laughing as well. It feels like a organic continuation of this film series. One thing however that let the film down, was the fact that the segments that involve Scrat have been used for similar purposes before and as such, the ones used in this film seem dated and boring, no more does the joke bring about the laughs that they used to. Although many people will not be bothered by this overuse, those who wanted a film that was entirely fresh will notice this issue. Saying that, however, these scenes do the job of fitting this film in with the rest of the franchise.
Following suit of the other movies, in regards to having narratives that revolve around factors associated with the last major Ice Age; the beginning of the Ice Age (1st), the melting of the ice (2nd) and the reappearance of dinosaurs that were thought to be extinct by the time the age started (3rd). This film follows this formula with focus shifting to the movement of the earth's plates and the forming of the continents. For this film however the reason behind this shift is played with, with Scrat taking credit by once again trying to bury his beloved acorn. It is a nice way to create a narrative for the principle characters and allows the film makers to create a story which will keep the audiences engrossed.
All characters that have appeared throughout the series return, with new spots open for Sid's deranged and decrepit old grand-sloth (spoken by voice-over pro Wanda Sykes), a grown up Peaches (Keke Palmer), her best friend Louis (Josh Gad). This brings the principle cast to nine, therefore adding much to the groups dynamic. On bad guy duty this time around is Captain Gutt (surprising voice work from Peter Dinklage) and his band of Sea Trotting Pirates, including the Sabre Tooth Shira (Jennifer Lopez), a love interest and possible femme fatale for Diego. Adding all these characters to the mix gives Ice Age 4 enough growth to allow the development team to create a story that is not only character driven, but highly entertaining. With a cast that includes such talent, it is not surprising that this film is able to produce perfect character voice work. Returning actors achieve very much what they did in the previous film and those that have been added, deliver to the same standard which in turn, incorporates together in a way that they always feel part of the series. This is credit to the casting team.
The inclusion of pirates into the plot, and the shifting of the plates, adds enough to the story but follows the formula of the other films. Again, credit to those responsible for the creative decisions involved. It is worth mentioning the cameo appearance of Ice Age 3's Buck, which again brings all the films in together.
When compared to the original film, the animation of the studio Blue Sky has continuously got grander. Although it is not to the crispness that is found in the work of Pixar, the way that they have continuously developed their skill is colossal. Animal hair has never looked this realistic in animation, and the environments are created to a highly realistic and professional standard. This film will continue the progression of the studio, and the awareness that it rightly deserves in the type of filmmaking they set out to achieve. Those people who enjoy animation movies, will not be disappointed with what the film has achieved.
With three films already made within this series, doubters may well rise the question of what is the purpose of this film? These doubts are answered with the fact that people have found fondness with the characters, and through this fondness there will always be a narrative which can add to the depth that they hold. Returning more to the standard that was found in the stronger installments also means that new life has been brought to this series. Future installments will probably come from the success that this film will bring, and with the development of these installments, hope is asked for the film makers to adapt the repeated joke sequences into something that is fresh. Scrat needs more to do, and if these parts are changed then the franchise can only get stronger. Overall a fun family film.