The special marks the first time the majority of the cast of the iconic franchise's eight films has reunited since the release of Harry Potter and the Deathly Hallows Part 2 in 2011.
While discussing the franchise's fourth film, Harry Potter and the Goblet of Fire, the cast talks about the heightened teenage hormones going around the set at the time of filming and within the paralleled storyline.
"There was crushes and people went out with each other and broke up, just like you used to do at school. It was exactly the same environment, but it was just in a Defense Against the Dark Arts class," shared Matthew Lewis, who played Neville Longbottom in the films.
Even Harry Potter himself, Daniel Radcliffe, talked about how he and Watson, who played his character's bestie, Hermione Granger, used to use one another for dating advice.
"The amount of prep and coaching Emma and I would give each other on texting to the opposite sex, like, if she was texting a boy or if I was texting a girl, I'd be like, 'She sent me this many kisses back. What do I do? This is a nightmare,'" he recalled.
"We had that kind of older brother, younger sister thing," Watson said of herself and Radcliffe.
But when the topic of the sparks between Watson and Felton, who played the villainous Draco Malfoy, came up, the two co-stars admitted that there was something more between them.
"Emma and I have always loved each other, really," Felton admitted in an aside interview.
Watson explained the moment she first fell for Felton when they were kids and doing on-set school tutoring together.
"I walked into the room where we were having tutoring. The assignment that had been given was to draw what you thought God looked like, and Tom had drawn a girl with a backward cap on a skateboard," she recalled. "And I just don't know how to say it, I just fell in love with him."
Watson went on to express just how infatuated she became with her co-star.
"I used to come in every day and look for his number on the call sheet, it was number seven, and if his number was on the call sheet, it was an extra exciting day," she admitted. "He was three years above me and so for him, he was like, 'You're like my little sister.'"
Felton added, "I became very protective over her, yeah, I've always had a soft spot for her and that continues to the day... There's always been something that's like, I don't know, a kinship."
Watson added, "I think really the truth of it was Tom was the one I could often be more vulnerable with."
But for those who think that all this admiration and adoration led to something more, Watson insisted that it simply never happened.
"Nothing has ever, ever, ever happened romantically with us. We just love each other. That's all I can say about that," she said.
Harry Potter 20th Anniversary: Return to Hogwarts is streaming now on HBO Max.