Crystal and her reptilian companion Amber (who took on the form of a Golden Retriever) had their first indirect encounter with the Mystery Inc. gang when making a landing run in Roswell, New Mexico (the Mystery Gang spotted their ship from the Mystery Machine and went off road in surprise).
Shortly after landing and beginning documentation of the planet, Crystal and her companion received word of sightings of other alien visitors who were not being as discreet and were actively abducting local fauna. She took it upon herself to investigate and when Shaggy Rogers invited her to join in their investigation, she agreed.
Crystal and Shaggy got rather close with Shaggy holding a romantic interest in her, while Amber and Scooby-Doo got close as well. When the alleged "invaders" got close to capturing Shaggy and Scooby, the two extraterrestrials discarded their false forms via the Peace Sign necklaces they both wore and frightened the "invaders", who were then caught.
Shaggy and Scooby were the only two members of the Mystery Gang to learn about Crystal and Amber's real identities, and the four parted ways after the investigation. Shaggy and Scooby kept this secret throughout their subsequent adventures.
- Scooby-Doo and the Alien Invaders (2000)