Mary Tyler Moore may have been the one who turned the world on with her smile, as Moore's sitcom theme has it, but co-star Georgia Engel helped make sure viewers' grins never faded into frowns.

Engel is best known for her role as soft-voiced Georgette Franklin, the sweet, ever-so-innocent girlfriend and later wife of self-important TV anchor Ted Baxter (Ted Knight) on one of the best sitcoms ever, "The Mary Tyler Moore Show."

Engel died Friday at age 70 in Princeton, New Jersey, said John Quilty, identified as her friend and executor by the Associated Press. Quilty said the cause of death was not known because she was a Christian Scientist and did not visit doctors, according to AP.

Younger viewers may know Engel as the mother-in-law of Brad Garrett's Robert on "Everybody Loves Raymond," and she also appeared in recurring roles on "Coach," the soap "Passions," and, more recently, in "Hot in Cleveland," which reunited her with "Moore" castmate and friend Betty White.

White, 97, offered a concise, sweet tribute to Engel Tuesday on Instagram: "'Friends Forever' says it all." The accompanying picture features the two with an affectionate bear friend in the middle. White is renowned for her commitment to animals.

Engel spoke about White's friendship and infectious love for animals at a 2018 Television Critics Association panel that focused on a PBS special celebrating White's impressive career.

"Betty is one of my dearest friends, and so it was a special joy when I got to be on 'Hot in Cleveland' with her," Engel said. "But my favorite times with Betty don’t have to do with show business. She opened adventures with animals to me, and I’ve had the most wonderful time getting to know animals through Betty’s love of them."

Ed Asner, who played gruff, lovable Lou Grant on "Mary Tyler Moore," also honored Engel Tuesday via Twitter: "My sweet Georgia. What a tremendous loss. The perfect mix of talent and kindness. With a sprinkle of perfect comic timing."

Despite a successful, long-running career, which included 2018 appearances in Netflix's "One Day at a Time" and a theater musical, "Half Time," Engel will always be best known as the sweet, gullible but subtly wise Georgette, the kind of true friend everyone can use. Engel apparently was a good friend in real life, too, as she maintained bonds with her "Moore" co-stars over the years.

Engel, who had a background in musical theater but only a couple of TV credits when she first appeared on "Moore" in its third season, admirably jumped aboard the smooth-running sitcom – no easy feat – and established herself among a cast of stellar veterans, including Moore, Knight and Asner.

Engel and White, who played naughty happy homemaker Sue Ann Nivens, helped the popular comedy, which ran seven seasons from 1970 to 1977, transition supporting players as original cast members Valerie Harper and Cloris Leachman went off to their own spinoff comedies on the power of the "Moore" show's success. Their predecessors left big shoes and Engel and White filled them admirably.

White's scheming, lustful Sue Ann, a master of mean-spiritedness behind a fake smile, became more of a breakout character, but Engel performed an impressive and perhaps more difficult task with Georgette, who had to fill part of the best-friend void created by the departure of the Harper's beloved Rhoda Morgenstern.

Fortunately, producers didn't try to make Georgette a carbon copy of the knowing, tart-tongued Rhoda. In Georgette, they wrote – and Engel embodied – an entirely new character on the show: an angelic, guileless woman whose lack of savvy seemed less the result of ignorance than of supreme innocence.

Georgette was less central than some of the other characters, but Engel obviously made a strong impression on her acting colleagues, earning two Emmy nominations for supporting actress. (She later received three guest-actress nominations for "Raymond.")

Georgette's lack of sophistication and misunderstanding provided plenty of laugh lines, but she was never the butt of the joke and Engel imbued the character with a wisdom regarding life that isn't found in textbooks.

It likely wasn't wisdom, but forbearance, that explained why she stuck with a pompous clod like Ted, whose obliviousness to his own flaws was one of the show's best and longest-running laugh lines. And, compared to Ted, anyway, Georgette could seem like a genius.

Georgette and Ted eventually married (with vows administered by a young John Ritter). They adopted a boy and later Georgette became pregnant and had a daughter.

Engel got together with Moore, White, Harper and Leachman for a memorable 2013 reunion on "Cleveland." It was great seeing the all-star team together but also sad, as Harper was facing life-threatening cancer (fortunately, she's still with us) and Moore, who suffered from diabetes, was in physical decline. She died in 2017.

After "Moore," Engel joined White on "The Betty White Show," a short-lived sitcom, before moving on to other roles over the decades, including guest appearances on "the Office" and "Two and a Half Men" and a role in "The Drowsy Chaperone" on Broadway.

She expressed her gratitude to White for helping her at the TCA panel.

"After 'Moore' ended … everybody went off to do their own spinoffs, and I found out later Betty said, 'Well, what about Georgia?'" Engel said. "And so she took me along with her. It was a short-lived series, but it just speaks to Betty’s self-forgetfulness."

It also speaks to Engel's value as a friend, a characteristic that apparently applied to the woman as well as her memorable character. And, thanks to TV reruns, she can remain that friend to viewers, too.

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