See Pauley Perrette's First Scenes as Abby Sciuto in 'JAG' and 'NCIS'

On Tuesday, Abby Sciuto will leave the cast of NCIS for good, leading some nostalgic fans to revisit her first appearance on JAG over 15 years ago.

NCIS itself began a spin-off of JAG. The core cast and premise were introduced in JAG's eighth season. That includes Abby, the laid back yet brilliant forensic scientist working for the Naval Criminal Investigative Service alongside Leroy Gibbs and the rest of the crew.

In season 8 episode 20 of JAG, Abby was introduced as an eccentric young woman who loved her job in the lab. She had put up colorful prints of some of her most grizzly x-rays, which she discussed with cool detachment.

After the NCIS cast appeared on two episodes of JAG, they were given their own time-slot. The cross-over was done as a backdoor pilot, prompting fans to get invested in the show right away, and it seemed to work.

NCIS was developed by Donald P. Bellisario, the creator and executive producer of JAG. The shows only crossed over two more times in their tenure. While JAG lasted a total of ten seasons, NCIS is now going strong in its 15th, and has spawned two spin-offs of its own.

Now, however, the beloved crime drama will change forever. After a decade and a half delighting fans with her quips and insightful eye, actress Pauley Perrette is stepping aside, and Abby must go with her.

Perrette announced her departure in October of 2017 through a post on Twitter.

"So, it is true that I am leaving NCIS after this season. There has been all kinds of false stories as to why (NO I DON'T HAVE A SKIN CARE LINE AND NO MY NETWORK AND SHOW ARE NOT MAD AT ME!)," she wrote frankly. "It was a decision made last year. I hope everyone will love and enjoy EVERYTHING ABBY not only for the rest of this season but for everything she has given all of us for 16 years. All the love, all the laughter, all the inspiration… I love her as much as you do."

Perrette did not offer much more detail as to why she was making this massive transition in her life. though she did tell TV Guide that it was a soul-searching decision.

"I believe in God and the universe so firmly, and it just suddenly became blindingly apparent that now was the time," she said. "After a lot of thought, I decided to announce it myself on Twitter because I didn't want it to be turned into anything 'shocking.' Abby leaving is more than a cheap TV ploy."