CBS continues The Big Bang Theory craze by ordering Young Sheldon Season 3 and Season 4 earlier than expected. The network assures the spinoff series' return for two seasons as the show is now included until its 2020-2021 TV lineup.

As The Big Bang Theory is about to come to completion, Young Sheldon Season 3 will take its throne by securing its Thursday night schedule. The long-running sitcom timeslot will be taken by its prequel series starting in the fall of 2019.

"Our new lineup features both classic CBS shows and genres that viewers love, as well as some new series that push the boundaries of what you might expect from us," CBS Entertainment President Kelly Kahl said in a statement, via E! News. "We are also saving some very strong series for the second part of the year as part of a strategy to roll out new and returning series throughout the season."

Young Sheldon Season 2 has an average of 11 million weekly viewers and a 1.8 demo rating. It takes the third spot of CBS's most-watched series after The Big Bang Theory and NCIS. In Live+7 DVR playback, it earns 15 million viewers and a 2.7 rating.

Kahl praised creators Chuck Lorre and Steve Molaro for their "outstanding creative leadership" that made Young Sheldon a powerful performer for CBS. Programming Senior Executive VP Thom Sherman, on the other hand, also commended the stars that portrayed the Coopers family's characters. He is even looking forward to seeing the writer's mine Sheldon's backstory and the family's dynamic in Young Sheldon Season 3, per TVLine.

Meanwhile, in Young Sheldon Season 2 finale, fans are about to witness a major The Big Bang Theory crossover. The show will give homage to the original series. After The Big Bang Theory Season 12 finale, the prequel will feature the younger versions of Leonard, Penny, Howard, Raj, Amy, and Bernadette.

A CBS rep confirmed the appearance of the young The Big Bang Theory characters in Young Sheldon Season 2 finale, although it is not yet revealed how it would happen. It is said to be part of the spinoff series' storyline, so it remains to be seen how their lives would coincide at their young age.

So, fans have to wait and see how the young Sheldon would meet the kid versions of Leonard, Penny, Howard, Raj, Amy, and Bernadette in Young Sheldon Season 2 finale. The final episode, titled "A Swedish Science Thing and the Equation for Toast," will be out on Thursday, May 16, at 9/8c on CBS, while Young Sheldon Season 3 release is yet to be revealed.