"The Big Bang Theory" is set to welcome a new member of the cast who is set to make things about the gang more interesting particularly Leonard and Penny's intensifying relationship.

TV Line got word that Jim Parsons, Johnny Galecki, Kaley Cuoco-Sweeting and the rest of the TBBT cast would be joined by a new face who would act as the "kerosene" to the series' fiery ninth season set to premiere on Sept. 21.

According to the outlet, the new character who would be portrayed by "Mom" star Melissa Tang, is someone from Leonard's (Galecki) past who has the power to "put a crimp" in his potential honeymoon with longtime on-screen girlfriend Penny (Cuoco-Sweeting).

Tang, who had already been chummy with quite a number of TV show guesting, had appeared in other series such as the CBS's classic comedy "How I Met Your Mother" and the Zooey Deschanel-starrer "New Girl."

Born in Los Angeles, California in May 1985, Melissa Tang began her acting career in 2006 when she starred in the film "The Routes of Wild Flowers," Buddy TV revealed.

Her TV career then hit off, leading to her being cast in different genres of TV shows including "The Unit," "CSI: Crime Scene Investigation," "Lie to Me," and "Harry's Law."

As her latest acting venture, Tang would first appear in the second episode of the ninth season as Mandy who had been dubbed by Variety as Leonard's "other woman."

According to TV Line, Leonard and Mandy canoodled while the former was on an expedition along the North Sea.

The 30-year-old American actress is set to appear in the second episode of the show's new season right after the comedic gang picks up from where eighth season of "The Big Bang Theory" ended: Penny and Leonard heading off to Las Vegas to finally make their relationship official by tying the knot.

Unfortunately, Penny's discovery of Leonard's lip-lock escapade has the worst timing ever, as it has been written to occur on the night prior to the couple's trip to the Sin City.

Cinema Blend revealed how it all happened during the season 8 finale cliffhanger when Leonard admitted to cheating on Penny while he was on expedition, noting that while the couple's relationship had not been solid at the time, it was pretty clear that he was dating her.

The outlet further cited how the revelation was not only untimely, but had been a shock both to Penny and the audience who were able to watch their relationship's ups and downs.

Now, the show's creators proved that they want to push through with this plotline as they introduce the woman whom Leonard cheated Penny with.