Rasmussen, known more colloquially as Raz, was a rough kangaroo that joined up with the piratical ape Gutt.
Raz worked under the command of a seafaring ape named Gutt, who voyaged through the seas in a massive glacier he dubbed his "ship"; Raz carried out her captain's orders with relish, enjoying fights as they arose.
Raz was rescued by Gutt from an unknown fate, earning her a spot on Gutt's pirate crew, which she filled loyally as the ship's weapons expert, filling her pouch with bone spears and daggers, which she would pass on to her crewmates during battle. She would also launch iceballs out of the ship's "cannons" using her feet.
One day, as the ship was out at sea, Raz and the rest of the crew watched as Gutt hoisted up the catch of the day: after harpooning a bone arrow into the waters, he pulled out a saber-tooth squirrel named Scrat, who had been holding onto an acorn fragment that Gutt had speared, who had been halfway swallowed by a fish, with a small scallop on his chest, and seaweed atop his head, was welcomed by Gutt himself, to the crew's amusement, Raz pointing her conch-shell spear at the squirrel and laughing along with the crew.
Not long after, the ship sailed on towards a small iceberg that Silas had spotted, containing four castaway animals: a mammoth, two sloths and a saber-tooth tiger. The crew watched the castaways with amusement, none more so than Raz, who claimed she would take the mammoth on in a fight, but like the others in the crew, she refrained from open attack until Gutt, the captain and leader of the pirates, made himself known. Gutt gave the castaways chance to surrender before having his crew open attack on the castaways, Raz filling her role by throwing the other pirates weapons from her pouch and firing the log cannons with ice boulders at the iceberg and soon after impeding the mammoth, named Manny, from escaping by pointing her conch-shell spear at him.
The four castaways had been captured and taken aboard the ship, where they were bound and tied with vines, and they, along with the squirrel caught earlier, were kept aboard as amusement. At that, Gutt introduced himself to the castaways.