By Gillian Telling
Updated October 12, 2015 at 12:00 PM EDT
Everett Collection

Before Julia Roberts, before Meg Ryan, there was Mary Tyler Moore — one of America’s first sweethearts, the girl with the mega-watt smile who became the poster child for independent, working women on TV in the ‘70s. On Tuesday, PBS will honor Moore and her lifetime of work with the documentary Mary Tyler Moore: A Celebration — 45 years after The Mary Tyler Moore Show made its debut in 1970.

Colleagues and friends like Carl Reiner, Dick Van Dyke, Valerie Harper, Cloris Leachman, Betty White, Tina Fey, and Oprah Winfrey all chime in on the documentary to tell their best Mary Tyler Moore anecdotes, while the actress relays her own memories about her television career, which first took off when she was cast as the wife Laura on Carl Reiner’s Dick Van Dyke Show in 1961 — several years before she fronted her own series as Mary Richards, an associate news producer in Minneapolis.

“I met her on television!” Valerie Harper tells EW about her first encounter with Moore, years before she was cast as Rhoda in Mary Tyler Moore. “I was watching her like the rest of the world on the Dick Van Dyke Show…she was adorable. She was so cute in those tight little pants, and classy—a very classy lady. And a brunette! I loved that! I used to come home from high school and watch the show, and then when they called me and said we think you might be good as her friend Rhoda, I was like, well that sounds very good.”

The documentary also takes a look at Moore’s very early career as a dancer, and touches on some of the hardships she faced growing up with an alcoholic mother. But mostly it highlights her excellence as a comic actress. “I wasn’t a comedian,” Moore says. “I was an actress who could do comedy.” (Some of the funnier clips from Dick Van Dyke and MTM show are shown to hammer home the the point.)

“There’s no BS from Mary,” co-worker Gavin MacLeod says in the documentary. “She is fun. As you can see from some of the scenes she has played in the show, she has an enormous sense of humor.”

As Harper says about her days working with Moore, “That whole set was really copacetic. It was all fun. We laughed so much, but we really worked very hard.” In the documentary, she also notes how kind Moore always was, and how she’d let Rhoda have the funnier lines all the time, just because she thought they suited Rhoda better.

“She’s an incredibly generous girl,” Harper tells EW. “She’s really just a great person.”

Click below for a preview of Harper in the documentary.

Mary Tyler Moore: A Celebration premieres Tuesday, Oct. 13 at 8 p.m. ET/PT.