Watch "The Big Bang Theory” Season 9 Episode 13 Live Stream Online; Gang Goes To Las Vegas?

(Photo : Smallz & Raskind / Getty Images Entertainment) LOS ANGELES, CA - JANUARY 6: (L-R) The actors of 'The Big Bang Theory' Kaley Cuoco, Johnny Galecki, Jim Parsons, Melissa Rauch, Kunal Nayyapose, Mayim Bialik and Simon Helberg pose for a portrait at the 2016 People's Choice Awards at the Microsoft Theater on January 6, 2016 in Los Angeles, California. (Photo by Smallz & Raskind/Getty Images for The People's Choice Awards

Watch "The Big Bang Theory" season 9 episode 13 live stream online here and here.

A preview video of episode 13 of the hit CBS series "The Big Bang Theory" season 9, titled "The Empathy Optimization," shows Penny (Kaley Cuoco), Leonard (Johnny Galecki), Bernadette (Melissa Rauch), Howard (Simon Helberg), Raj (Kunnal Nayyar) and Emily (Laura Spencer) planning to leave on a weeklong trip to Las Vegas on a party bus, reported IBTimes.

However, the group plans on leaving Sheldon behind because of his annoying attitude. When Sheldon comes to know about the plan, he will apologize to each of his friends hoping that they will consider him to accompany them on the Las Vegas trip.

In the teaser released by CBS, Sheldon approaches Leonard and asks him to be ready for his much-awaited apology.

"Leonard, get ready for an apology," he said, according to Design N Trend.

The next scene shows Sheldon making an apology to Penny while she is taking a shower in the bathroom.

"Can this wait?" Penny asked him.

"I'm afraid it can't. I have more apologies to make," Sheldon replied.

Sheldon will also be seen apologizing to Raj and gifting Bernadette and Howard a pair of custom made "Sheldon Cooper Apologized To Me" t-shirts, as expected in "The Big Bang Theory" season 9 episode 13 live stream.

In the last episode titled "The Sales Call Sublimation," Penny told the new therapist, Dr. Gallow (guest star Jane Kaczmarek), that living with Sheldon stresses her out too much. In fact, she blamed Sheldon for many of her problems with Leonard.

"Not only am I Leonard's mother, but we have this man-child living with us," Penny complained.

"Leonard told me a lot about him," Dr. Gallow continued. "I wasn't sure he was real."

"Oh, he's a real as the fine I have to pay for using too much toilet paper," Penny replied.

Don't forget to watch "The Big Bang Theory" season 9 episode 13 to know if the gang goes to Las Vegas without Sheldon. "The Big Bang Theory" airs Thursdays at 8 p.m. EST on CBS.

Fans can watch "The Big Bang Theory" season 9 episode 13 live stream online here and here.