Kaley Cuoco Posts Lingerie Snap On Instagram Before 'Big Bang Theory' Finale [PHOTO]

"Big Bang Theory" actress Kaley Cuoco and her co-stars are counting down the days before the finale of the long-running CBS series and are enjoying their last weeks of filming together.

On Instagram, Cuoco recently shared a photo of herself posing in lingerie with "Big Bang Theory" co-star Johnny Galecki on the set of the comedy show. In the snap, Cuoco, as her character Penny, points at Galecki, who plays the role of Leonard, as the latter makes a pained expression.

In her caption, Cuoco implied that she hadn't been allowed to post the funny photo until the day "Big Bang Theory" Season 12, episode 15 aired. She also joked about spending the entire episode dressed in lingerie but clarified that she only wore it for one scene with Galecki.

Prior to this, Cuoco also shared another photo from the set of "Big Bang Theory" Season 12 on Instagram. The snap showed her embracing "Star Trek" actor William Shatner, whom Cuoco called "one of [her] favorites of all time."

Shatner is set to appear in "Big Bang Theory" Season 12, episode 16, "The D & D Vortex," along with "True Blood" alum Joe Manganiello, NBA legend Kareem Abdul-Jabbar and director Kevin Smith.

In the "Dungeons & Dragons"-themed episode, Sheldon (Jim Parsons) and the rest of the gang will do whatever they can to participate in a game hosted by Wil Wheaton.

"The gang finds out Wil Wheaton hosts a celebrity Dungeons and Dragons game involving William Shatner, Joe Manganiello, Kareem Abdul-Jabbar and Kevin Smith. Deception and betrayal are the path to make it to the one open seat," the synopsis of "Big Bang Theory" Season 12, episode 21 read (via TV Guide).

Meanwhile, Shatner will not be the first "Star Trek" vet to make an appearance on "Big Bang Theory." George Takei briefly appeared in Season 4 while, in Season 5, the late Leonard Nimoy lent his voice to a Spock action figure that spoke to Sheldon in his dreams in the episode "The Transporter Malfunction."

Brent Spiner and LeVar Burton from "Star Trek: The Next Generation" have also cameoed on the show, and Wheaton has recurred as himself since the third season.

Catch Cuoco, Galecki, Shatner and the rest of the cast when "The Big Bang Theory" Season 12, episode 16 airs on Thursday, Feb. 21 at 8 p.m. EST on CBS.