In 1996, Birds & Animals Unlimited, the largest furnisher of animals to Hollywood, sent one of its trainers to purchase a capuchin monkey in Florida. Birds & Animals prefers to begin training younger monkeys, optimally those close to one year old. Audacious two-and-half-year-old Crystal, whose canine teeth had begun showing, was offered. The trainer ultimately decided to buy both Crystal and two younger capuchin monkeys. Three employees received the three monkeys. Crystal was given to Tom Gunderson, an employee who had only been with the company for a few years and had been primarily working at Universal Studios Florida's Animal Actors stage show. Gunderson had let the other two employees select their monkeys first and was left with the oldest, Crystal. He named her Crystal, a namesake to a country music singer Crystal Gayle. New York magazine's Benjamin Wallace wrote, "It was like she was born to perform."

She is known for her roles in the 2006 film Night at the Museum and its sequels, Night at the Museum: Battle of the Smithsonian (2009) and Night at the Museum: Secret of the Tomb (2014), playing troublesome monkey Dexter (also playing another character, Able, in the second film). In the 2009 film, her character slapped Ben Stiller's, while her trainer encouraged her with "Get him! Get him! Hit him harder! Hit him harder!" Stiller joked that "I really dislike the monkey. There's no way to feel great about having a monkey slap your face on any level." During filming, Crystal in an "unscripted moment" relieved herself on Robin Williams, who was playing Teddy Roosevelt. Williams said, "It combines the worst aspects of working with children and animals when you have an animal that looks like a child ... Plus, what human can [defecate] on you in the middle of a scene and people would be like 'Awww, great'".

In 2011 she played Donald the Monkey in the Frank Coraci-directed film Zookeeper and was voiced by Adam Sandler. Crystal also played Crystal the Capuchin in the Cameron Crowe-directed film We Bought a Zoo.

She played Dr. Rizzo, a crony of misanthropic Veterinarian Dr. George Coleman in Animal Practice, a sitcom that debuted on September 26, 2012. Before the show was cancelled due to low ratings, Crystal netted her owner $12,000 per episode; the earnings from nine episodes meant that for the year she made more than twice as much as the average Hollywood actor. New York's Wallace observed the filming of a scene in which Crystal gives Coleman a shoulder massage. Gunderson used gestures to coax Crystal to perform the desired action and let her lick yogurt from his fingers upon finishing. After each scene, Gunderson rewards her with a treat. Wallace noted that her favorite treats included "chocolate, Nutella, grapes, pistachios, peanuts, the odd crafts-services Banana, a weekly egg for protein, and, off-set, spiders and flies".