Serena Williams' husband Alexis Ohanian in awe of Qai Qai's massive social media influence

Serena Williams' popularity shows no signs of waning post-retirement. The tennis legend has been delighting her fans off the court as well, with her daughter Olympia's doll recently taking social media by storm.

Made popular thanks to The Adventures of Qai Qai, a children's picture book that Williams recently authored, the doll now has 4,000,000 followers as per a tweet from her husband Alexis Ohanian.

"4,000,000 followers. That's more followers for my daughter's doll on one social media platform than I have on all of mine COMBINED (I'm only at 1.6M). Impressive, QQ," Ohanian tweeted.

The book, which was released on September 27 got off to a flying start, making its way to the top of Amazon's list of new best-selllers.

During an interaction on ABC's Good Morning America, Williams asserted that although her daughter feels the book is about her own family, in reality the story is a work of fiction.

The tennis star also revealed that she wanted the doll to represent a black girl.

"When I saw the illustration I said listen I really wanted to represent a black girl because I thought it was really important and that was the reason Qai Qai came on because I was looking for a black doll and I wanted it to be something really authentic. She (Yesenia) did a wonderful job with getting that across even with the mom and the dad and it's an amazing family in the book so," Williams stated.

"Watching Serena Williams has been such an amazing experience growing up as a child, especially because of how proudly she wears her hair" - Yesenia Moises

Serena Williams has been one of the most flamboyant players of her time

Yesenia Moises, who illustrated the book, The Adventures of Qai Qai, recently told the BBC that she had an amazing experience watching Serena Williams as a child, especially because of how "proudly" she wore her hair.

"Watching Serena has been such an amazing experience growing up as a child, especially because of how proudly she wears her hair," Moises said. "When she was younger she would wear the beads, the braids, and I thought that was really cool. In the 90s and early 2000s, that wasn't really common because the image of a black person on TV was usually that of someone with straight hair or hair that looked a little tamer."

The Bronx-based illustrator also recalled the moment she received an email requesting her to work on the illustrations for the The Adventures of Qai Qai.

"It still doesn't feel totally real. Sometimes I pinch myself and I'm like, 'Did this really happen?'" Moises added.

Serena Williams, who played her last professional match at the US Open earlier this year, has featured in numerous movies, television shows and commercials over the years.