Sheldon and Leonard get in a heated debate that will eventually involve everyone in "The Big Bang Theory" season 9, episode 21, titled "The Viewing Party Combustion."

According to spoilers, the two best buds will argue about their roommate arrangement meeting. Sheldon believes they should continue holding those affairs while Leonard does not want to go to one anymore.

[Spoiler Alert! Plot details about "The Big Bang Theory" season 9, episode 21 below]

As the argument goes on, Penny, Amy, Bernadette, Howard and Raj somehow get involved and are forced to take sides, although Howard and Raj are fighting about the latter bragging about dating two ladies.

Looking at the promotional photos for "The Big Bang Theory" season 9, episode 21, the two camps that form out of the group stay in different rooms – 4A and 4B. Penny seems to have taken Sheldon's side while Leonard gets Amy's back in the argument.

Along with Penny and Sheldon are Raj and later Stuart, who is tricked by Howard into dressing up for a nonexistent costume party. This leads him to join Penny and Sheldon's camp.

Revelations came out of Leonard and Sheldon's debate. In "The Big Bang Theory" season 9, episode 21, Amy will reveal to Leonard how she truly feels about roommate arrangement meetings and how they seem to make Sheldon and Penny so close.

The dispute sees no chance of ending if it weren't for Howard, who has to be taken to the hospital after Leonard serves peanuts to the viewing party, which he was not supposed to eat. On a side note, the viewing party is all about "Game of Thrones."

The gang rushes to the ER including Bernadette, who goes home and opted out of the fight early on. This eventually helps the group settle aside their differences.

"The Big Bang Theory" season 9, episode 21, "The Viewing Party Combustion," airs April 21 at 8 p.m. ET on CBS.