[This piece contains spoilers for Younger season three.]

Lizzie McGuire and gravity were never friends. From falling in the cafeteria to wiping out at graduation, Hilary Duff's infinitely relatable character perfected the art of tripping over thin air. Yet when Lizzie McGuire premiered in 2001, she also became one of Disney Channel's most cherished stars. Fans adored watching an extraordinarily average girl navigate middle school drama, embarrassing moments and all.

Fast-forward to today, and Duff's latest starring role is Younger's Kelsey Peters, a twentysomething book editor working her way up the publishing industry. From the outside, she's a picture of poise and grace. She dresses to the nines — no repeating outfits here — with sky-high heels that Lizzie probably wouldn't last five minutes in. So at first glance, Duff's most famous TV characters seem like polar opposites.

But as you get to know Kelsey, her insecurities come to light. Creator Darren Star, also the mastermind behind Sex and the City, makes sure you can "get inside her head" even without a cartoon's running commentary. I previously wrote about what Kelsey offers to fans (like me) who grew up watching Lizzie, so when I visited the Younger set in New York last month, I asked Duff if she sees the same similarities.

"When Darren reached out to me and sent me the script, I was like, ‘This is so up my alley,’" Duff told me about returning to series TV. In the decade between starring on Disney Channel and TV Land, she appeared on Gossip Girl, but mostly focused on romantic comedies, her chart-topping music career, and raising son Luca, 5. [Note: TV Land and MTV News are both owned by Viacom.]

"[Younger's relatability] is [similar to] what I loved about Lizzie McGuire," Duff said. "[Lizzie] was the relatable girl that everyone wants to be friends with, and that's who Kelsey is."

Molly Bernard, who plays Kelsey's ride-or-die best friend, Lauren Heller, agreed: "Kelsey models really great boundaries and support for her friends."

This loyalty is tested when Younger returns Wednesday (June 28). Forty-year-old mom Liza (Sutton Foster) has been pretending to be a 26-year-old publishing assistant, a lie that's unraveled more and more with each season. Kelsey and Liza have built the kind of friendship in which they tell each other everything, but this secret threatens that trust.

"The memories they've made have been tarnished now," Duff said about learning the truth in Season 3's cliffhanger finale. "Think about if you were friends with someone at your workplace and then all of a sudden they were like, ‘I'm 40 and I have a daughter.’ You'd be like, 'You're a psycho freak, what the hell?'"

Fortunately Kelsey can take her sweet time figuring things out, as the show's already been renewed through Season 5. "She's still flailing a little bit, but she is kicking ass and taking names," Duff said. "That's what I want for young people that are ambitious and maybe slightly still funky in their own skin. She's finding her way, but she's doing it, and I think that's what Lizzie McGuire would be doing right now."

So does Duff quite literally think of Kelsey as the grown-up Lizzie? "No, I don't!" she laughed. "I think Lizzie McGuire would be an intern still, like, dropping papers all over the floor."

"Yeah, she'd be a mess," Bernard added. Yet outside of the office, she pointed out, both characters illustrate realistic, dynamic friendships. "As modern actors, [it's] still our responsibility somehow to model behavior — oh, right, I've been in that situation at work, and this is how I did it, this is how she did it, I could learn from that."

Like Lizzie and Miranda, the Younger friends often get into tricky situations, though these days they're more R-rated than bra shopping. In one upcoming Younger scene, for example, they get "really stoned, walk into a room, and everything looks like the shape of a penis." But whatever life throws at them, it all comes back to playing the girl everyone wants to be BFFs with.

"It's nice to play a character on a show that's obviously way more adult and more where I am in my life but still [has] that relatability factor," Duff said. "That's been my fan base for so long and that's who I speak to as a person."

She's right. Lizzie tackled everything that went down in your school's hallways: first crushes, bad grades, yearbook signatures, cheerleading auditions. Sitting with the so-called popular kids won't solve the issues addressed in Younger, however. Between struggling with impostor syndrome at work and losing her fiancé, Kelsey proves that all grown-ups, to a certain degree, are just winging it.

"You can evolve and redefine who you are and what you want at any age," Duff explained. "It's about not getting too stuck where you are, because we're always allowed to evolve, and trying to have fun when you do it. It doesn't have to be so serious and so stressful all the time."

In other words, it's never too late to discover what your dreams are made of.