Sunday is the 20th anniversary of Ellen's historic "The Puppy Episode," when Ellen Morgan (Ellen DeGeneres) came out as a lesbian. In recognition of the anniversary, ABC is making that and all episodes of the sitcom available to stream on its app.

The two-part episode first aired April 30, 1997, about two weeks after DeGeneres herself publicly came out with her "Yep, I'm Gay" Time magazine cover. She was the first primetime lead on network TV to come out, and it was a huge moment in representation for LGBTQ stories on television.

It was also a huge cultural moment in terms of sheer numbers: an estimated 44 million people watched the episode. It went on to win an Emmy for Outstanding Writing in a Comedy Series and a Peabody Award.

Ellen DeGeneres and Oprah Winfrey, <em>Ellen</em>Ellen DeGeneres and Oprah Winfrey, Ellen

But more importantly, it was the most mainstream positive representation of a lesbian character there had been on TV at the time. It helped pave the way for the increased representation of minority stories on television we see now. Oprah Winfrey, who guest-starred on the episode as Ellen's therapist, called it a "seminal moment for anybody who was hiding behind anything."

It was also hugely controversial. Advertisers pulled out, right-wing religious groups protested, and there were bomb threats called in to the studio.

DeGeneres ended up facing a huge backlash, and the show was cancelled after the next season. But she's back on top now. She's one of America's most beloved and trusted public figures, the host of an immensely popular talk show, and Presidential Medal of Freedom recipient.

Ellen DeGeneres and Laura Dern, <em>Ellen</em>Ellen DeGeneres and Laura Dern, Ellen

"It's easy to forget now, when we've come so far — where now marriage is equal under the law — just how much courage was required for Ellen to come out on the most public of stages almost 20 years ago," President Obama said when giving her the award last November. "Just how important it was. Not just to the LGBT community, but for all of us."

She's done more than almost anyone to make America comfortable with the LGBT community, and "The Puppy Episode" is what started it all.

Ellen is available to stream for free on ABC.com and the ABC app in the Throwbacks section.