Deleted Role: The first movie was originally going to feature a female sloth named Sylvia, voiced by Kristen Johnston (Sally on 3rd Rock from the Sun), a Clingy Jealous Girl whom Sid was trying to get rid of. She was cut for various reasons, mainly because she made Sid come off as a Jerkass. Deleted footage with her can be found on the DVD release. For instance, the scene where Sid provokes Diego into pretending to bite him to scare off the two rhinos Carl and Frank used to involve Sylvia instead.
And in probably the best one of them all - Captain Gutt is voiced by Tyrion Lannister.
In the Bulgarian dub, Nikolay Urumov, who voices Diego, also provided the voice for Scar from The Lion King, and Tai Lung, the snow leopard from Kung Fu Panda.
Makes even more sense, because in the original English, Zeke is Jack Black!
In the German dub, Otto Waalkes plays Sid!!! It's one of the rare examples of the dub being better than the original, not only for the puns, but also for Otto's voice which is just funny to listen to, in and of itself.
The German dub also features Thomas Fritsch as Diego, who seems to be Germany's answer to the above-mentioned Nikolay Urumov (he's the German voice of Scar and Tai Lung as well), and Arne Elsholtz, the German voice of Bill Murray, as Manny.
In the fourth film, Diego's love interest is Dot Warner!
In the Spanish dub of the fourth film, Kim Possible is the only other female member of the pirates.
Those Two Actors: Simon Pegg and Nick Frost!... get seperated between the third and fourth movies...
Throw It In: John Leguizamo made up Sid's lisp after seeing a model for what he looked like.
What Could Have Been: The first movie was originally going to be directed by Don BluthandGary Goldman, and would have been traditionally animated. After Titan A.E. bombed, the 2D animation unit was demolished, and the film was given over to Blue Sky.
Before it was given to Blue Sky, Fox actually offered Disney the chance to make the film, but they turned the project down. If Disney had said yes then not only would Ice Age be entirely different, but Blue Sky Studios as we know it most likely wouldn't exist.
Buck was originally supposed to have been voiced by Harrison Ford, but he said no due to scheduling conflicts with the fourth Indiana Jones movie.
The fourth movie would've taken place in modern times with Manny, Sid, Diego, and Ellie being defrosted in a museum.
Diego was going to die at the end of the first film, but he survived in the final cut because it was too depressing for the kids in the test audiences. Denis Leary actually warned the producers that this would happen. When it proved true, he got his wish and Diego remained alive.