The Big Bang Theory star Kaley Cuoco has had an unexpected reunion with stars from a past television show.

The actress, who played Penny Hofstadter on the CBS sitcom, got her big breakthrough when appearing as Bridget Hennessy on 8 Simple Rules, which ran for three seasons between 2002 and 2005.

In a post on Instagram, the actress shared a snap with former co-stars Amy Davidson and Martin Spanjers, who played her on-screen siblings Kerry and Rory. The trio were attending a fundraiser in honour of John Ritter, who played their father on the show.

"Wonderful night supporting the @johnritterfoundation! It's a wonderful foundation spearheaded by the incredible @yasbeckamy … consider checking them out" Cuoco wrote in the caption to the photo, with Davidson commenting: "Such a wonderful evening. Love you sis."

Cuoco, who recently welcomed her first child with boyfriend Tom Pelphrey, will star in a new true crime drama, Based on a True Story, with the first images of the series being released earlier this week.

The eight-part series will focus on realtor Ava Bartlett (Cuoco) and her former tennis star husband Nathan (Chris Messina), who team up with a plumber (Tom Bateman) in order to cash in on the twisted craze.

The series, which is being created by The Boys' Craig Rosenberg, will serve as "a satirical look at America's dark obsession with the true-crime genre", the showrunner recently teased.

"Over the last decade, a true crime phenomenon has swept over America. Podcasts, documentaries, fictional shows based on true stories – they dominate the culture," he said. "Murderers have become celebrities and celebrities have become murderers, which inspired me to create this show.

I became fascinated with the idea of a relatable married couple whose youthful dreams hadn't come to fruition and who saw the true crime tidal wave as an opportunity to change their lives and save their marriage," he added, before explaining that the setting of Los Angeles would be vital in conveying the show's themes.