A source tells ET that the plan was for 41-year-old West to perform three songs, and he kept performing the third song -- "Ghost Town" featuring Kid Cudi and 070 Shake -- even after the show went off the air at 1 a.m. West then called the cast back on the stage after they left as he continued performing, which is when he began his rant. At that point, the show had been off the air for several minutes.
The source says West's wife, Kim Kardashian, as well as sister-in-law Kourtney Kardashian and their kids were all in the studio after the show ended. During West's unexpected comments to the crowd, the source says Kim just stared at him and didn’t seem fazed by it, although he did receive audible boos from the crowd. Other celebrities in the audience included Chris Rock -- who posted West's comments on his Instagram Story -- as well as Aziz Ansari and Jonah Hill.
West and Kardashian did not go to the after-party.
As far as West wearing his red "Make America Great Again" hat, the source says no one at SNL told Kanye not to wear it despite the rapper's claims that he was bullied by the show. In fact, West wore the hat during the show's promos with host Adam Driver and cast member Kenan Thompson.
"They bullied me," West said during his controversial comments over the weekend. "They bullied me backstage talking about, 'Don't go out there with that hat on.' They bullied me backstage."
According to the source, West asked people backstage if he should wear the hat or not. And despite the bullying comments, the source says West was nice to the crew, friendly with people backstage and even hugged crew members.
As for other backstage scoop, the source says singer Ariana Grande -- who was originally scheduled to perform for SNL's season opener but canceled following the sudden death of her ex-boyfriend, Mac Miller -- was backstage in her fiance, Peter Davidson's, dressing room supporting him for the season debut. The source says she kept to herself and didn’t show up with an entourage.
And when it comes to Damon's show-stealing performance as Kavanaugh, the source says the script for the SNL opener wasn’t written until Friday and was actually done very late. Damon flew in, arrived Saturday afternoon and went straight to dress rehearsal. They created Damon's look when he arrived at dress rehearsal.
SNL returns next weekend with host Awkwafina and musical guest Travis Scott.
ET spoke to SNL cast member Leslie Jones at the Emmys last month, where she admitted she didn't know if West would behave himself as musical guest. Watch below: