Crash and Eddie are the possum twins who are two of the leaders of the Sub-Zero Adventure Group.
Adopted brothers of Ellie, they cared for her and taught her to hang by her tail from a tree branch when she slept, as they did.
They first made their presence known to the opening characters by means of shooting pebbles(or possibly Spitballs) through reeds at Sid and Diego, then baiting them so as to humiliate them, but Diego began chasing them, leading both Sid and Diego to Ellie. After much persuasion, Ellie and her brothers joined Manny, Sid, and Diego, though Crash and Eddie spared almost no opportunity in bothering Diego. As they traveled with Manny and his friends, Ellie grew closer to Manny, putting both Crash and Eddie somewhat closer to Manny and his friends, but creating a short grudge when Manny tried "hitting on" Ellie. In time, however, they saw behind the petty grudges and worked together with Manny, Sid, and Diego to escape the flood, but left with Ellie when she left Manny and his friends to cross the minefield, as she claimed that it was suicide to cross it. Crash and Eddie joined Ellie in trying to escape the flood, but soon ran into trouble when they were trapped in a cave. Ellie insisted that they leave her to the point of pushing them outwards from a small crevice, but they promised to return with help, and true to their word, sought out Manny to try and free Ellie. They eventually made their way into a rushing current of water and were almost swept away when a foolish Sid came along to jump into the current, leaving them, in addition to holding onto a branch for dear life against the current of water, trying to hold onto an unconscious Sid. Diego eventually helped when he jumped in and saved them from drowning along with Sid. When Manny had saved Ellie from drowning, they helped Ellie back onto solid ground, but almost drowned when the flood was encroaching. Eventually however, the waters drained, leaving Crash, Eddie, and all of the others alive. When a herd of mammoths came by (as mammoths were presumed all but extinct), they thought that Ellie would go with them and leave Manny, so they went with her. But as it turned out, Manny and Ellie stayed together because they wanted to, rather than being obligated to, and so they left onwards with Sid and Diego, as well as Crash and Eddie.
In the third film, Crash and Eddie travel with the others to the dinosaur jungle to save Sid from Momma, and both grow to idolize Buck, the one-eyed dinosaur-hunting weasel who helped them find Sid. They also mentioned that they never liked Sid, but wasn't true because they helped Buck to save him when he was going to die.
All in all, they love each other very much as shown in both the films.
In Manny, Sid and Diego's Adventures of John Carter, they have Thark forms as they appeared on Barsoom of Mars (only Crash and Eddie).
They will make their guest appearances in other projects outside of the Manny, Sid, and Diego's Adventures Series, such as Danny Phantom's Adventures of Short Circuit 2 and several episodes of Captain Charles T. Baker's Adventures of Kim Possible.
Crash is voiced by Seann William Scott and Eddie is voiced by Josh Peck.