"It is my birthday and I need you to swear to it on Oprah," Randall says.

"I'm not doing that," Beth says.

But she relents. The swear on Oprah gets made. However, "Even Gayle lets Oprah down sometimes," Beth says behind Randall's back.

Expect to learn more about Beth this season, whether or not that includes what happens when you swear on Oprah remains to be seen. "We have some stuff coming for Beth right away early in season three where you really learn about her and where she comes from and what her background is that I think is going to be really exciting for the audience," series creator Dan Fogelman previously told E! News.

This Is Us returns Tuesday, Sept. 25 at 9 p.m. on NBC.

(E! and NBC are both part of the NBCUniversal family.)