Originally, the story was rumored to involve Manny, Sid, Diego, Ellie, and Scrat frozen solid and accidentally defrosted in a museum in present day. The movie was going to be called "Ice Age: Th4w".
When on the iceberg ship, Sid the Sloth says "water water everywhere, but not a drop to drink". This is from "The Rime of the Ancient Mariner", a poem written by Samuel Taylor Coleridge in 1798. The actual line from the poem, however, is "Water, water everywhere, nor any drop to drink."
Initially in production Gutt was designed as a bear, but in the end, Peter DeSève, the film's art director, settled on an ape, due to the ape's flexibility and four hands, which seemed more fitting to have him swinging on the ship's rigging.
Peter DeSève designed a number of animals for the film that never made it to the final cut: eohippus (prehistoric horses), a large horselike animal that Sid would have ridden, a giant squid and a number of prehistoric sharks that would have nearly eaten Granny in the scene in which she takes a bath in the ocean.
The trivia item below may give away important plot points.
When the waters surrounding the island of Scratlantis sink into the earth, forming North America, a snippet of Samuel A. Ward's "America the Beautiful" sounds.