Accidentally Correct Writing: In "Giant of the Skies", the tapejarids are depicted as having black bodies and red crests. In 2017, a tapejarid was discovered with preserved melanosomes (pigment cells). Guess what colors its body and crest were.
Accidentally Correct Zoology: The dromaeosaurid from "Death of a Dynasty" was seen as an example of Anachronism Stew, as Dromaeosaurus (what the animal was called during production despite its flaws) was extinct by the K/Pg extinction. Skip ahead to 2015, and a dromaeosaur just the right size to match with this creature was discovered in the exact formation the episode takes place in (Dakotaraptor).
Humorously enough, his Ice Age costar, Ray Romano was picked to host the Discovery Channel premier of "Walking With Beasts" in order to promote Ice Age.
Executive Meddling: For the Walking with Dinosaurs movie, 20th Century Fox decided to add voices to the dinosaurs to help kids get the film, but the decision was made really late in production to the point where there isn't even lip syncing. The majority of viewers disliked the change, as they found the voices annoying and distracting. The DVD thus contains a "Cretaceous cut", which cuts out all the voices.
Every post-WWD toy of Liopleurodon has been given the colour scheme it had in WWD.
Orphaned Reference: The 'Cretaceous Cut' (the dialog-free version) of The Movie leaves in a few gags that make no sense without dialog:
In the theatrical cut, Alex explains some gorgosaurus stats to the viewer with close up shots and diagrams (and he keeps getting distracted by its tiny arms). The visuals for this scene are left in the Cretaceous Cut.
The film gets inexplicably re-wound when Patchi falls in the river (originally, Alex questions Patchi's claim of diving in to save Juniper)
There is a close up of one of the knocked-out gorgosaurus teeth (which becomes the fossil in the present day scenes)
The closing credits pop music starts to fade in and is interrupted by the gorgosaurus fourth wall break, but the actual credits with that song have been cut.
Baryonyx and Cetiosaurus were to appear in the main series, but they were replaced with Utahraptor and scrapped entirely, respectively.
The Sea Monsters book describes a number of scenes that didn't make it into the series, such as the female nothosaurs leaving their eggs on the beach at night (there is also a picture of Nigel inspecting those eggs, meaning it was filmed) and Nigel meeting the utterly bizarre aquatic ground slothThalassocnus before going to look for the shark C. megalodon.