Barrymore felt she was in a "pressure cooker" when deciding on her first guests, she tells ET's Kevin Frazier. When Diaz and Liu popped into her head, she started crying.
"It felt so right," she explains. "I made them videos where I get on one knee, and I cry in the videos, making like, a marriage proposal to them."
Remembering her time making the Charlie's Angels movies with Diaz and Liu, Barrymore says her favorite memory is just how they became "so close." "[We're a] tripod and the three little bears that met and became magnets and we're still here together," she gushes.
"We have experienced life, love, death, birth, loss, gain, we have lived all of the different themes that life has in it, and so we want to explore that on this show," Barrymore continues. "I thought, 'Who else better to do that with than two women I have been doing that with for 20 years?'"
"They're my girlfriends. I don't need to be formal, but it just felt like a big deal, and really special," Barrymore says of asking Liu and Diaz to be on her show, noting that another longtime pal, Adam Sandler, will also appear. "Really the first day is almost a love letter from me to them, but I'm really excited about some of the surprises we have planned."
Reese Witherspoon, Billy Eichner, Jane Fonda, Gabrielle Union, Christian Siriano, Charlize Theron, Tyra Banks and Billy Porter will also be featured guests on Barrymore's first week of shows -- and while fans might assume she runs in the same circles as her celeb guests, the mom of two says she actually doesn't hang out with a lot of famous faces.
"For someone who grew up in Hollywood, I don't hang out with fabulous people, I'm not out at dinner parties and events," she says. "I have the same friends that I've had for 30 and 40 years."
"I am just as excited to meet and speak with these people as if I wasn't in this industry," Barrymore adds.
The Drew Barrymore Show premieres Monday. Check local listings for showtimes and more information, and see more from our interview with Barrymore on Friday's ET.