On Friday, Bell shared a black and white selfie taken during the NCIS: LA Season 10 wrap party, with Elliott and camera operator Terence Nightingall.
"Who's excited for tomorrow night? Harm is back.... on NCIS: LA," Bell wrote in the caption, which was published before Sunday night's episode aired.
The photo earned more than 7,000 likes and hundreds of comments from JAG fans just itching to see the reunion more than a decade in the making.
"Looking forward to watching it. Always liked Harm and Mac characters. Glad they will be back. Hope they will be back more often," one fan wrote.
"So excited for Harm and Mac to make appearances!! My JAG loving heart is happy," another added.
"You and David have the best on screen chemistry. So excited to see Harm and Mac again," a JAG superfan wrote.
"Have DVR set for next 2 NCIS LA, I saw all 10 seasons of JAG," another fan wrote. "Would love to see reunion movie. I have no doubt Good Witch will return. Great Series, Great Cast."
Elliott's first appearance as Navy Captain Harmon "Harm" Rabb Jr. in 14 years aired Sunday night in "The Guardian." NCIS: LA team members Callen (Chris O'Donnell) and Hanna (LL Cool J) meet up with Harm aboard the U.S.S. Intrepid to track down a group of ISIS sympathizers.
The story continues in next week's episode, "False Flag," when Bell returns as Lieutenant Colonel Sarah "Mac" Mackenzie. Hetty (Linda Hunt) calls her in to help get information on a Russian diplomat.
There have been rumors that the two-part NCIS: LA Season 10 finale would also serve as a backdoor pilot for a JAG revival. However, CBS did not comment on it and the network did not announce a revival when it announced its new shows for the 2019-2020 TV season.
"Not only is it great to be working together again as friends, but to be able to write for Catherine and have her same character interact with our NCIS: Los Angeles characters now, that's wonderfully surreal. It feels like everything has come full circle," Bell said in a statement earlier this year.
The NCIS: LA Season 10 finale airs on Sunday, May 19 at 10 p.m. ET on CBS.
Photo credit: Getty Images/CBS