'Grey's Anatomy' Alum Kate Walsh Talks Possible Return in Season 16: 'I'm Sworn to Secrecy' (Exclusive)

Grey's Anatomy fans have been playing a guessing game ever since reports surfaced of a beloved main character's possible return in Season 16. Almost immediately, fans of the medical drama began to share theories on who it might be after the season premiere reveal of Amelia Shepherd's (Caterina Scorsone) surprise pregnancy. With the character's connection to spinoff series Private Practice, many shared their belief the storyline was the perfect excuse for Addison Montgomery, played by the inimitable Kate Walsh, to make a triumphant return to the show this season.

While catching up with Walsh exclusively for PopCulture.com to discuss her partnership with animal health company, Zoetis in honor of its new social media campaign raising awareness for allergic dog itch, the California native opened up about seeing the fan theories regarding her possible return, but kept her responses vague about whether an Addison cameo is actually on the horizon.

"Absolutely. Anything's possible," Walsh told PopCulture.com when asked if she would possibly return to the show some day. "If it's the right time and the right storyline, yes. I always considered Shondaland my home, and particularly Grey's. That's where it was just a big important piece of my life, and I love everyone involved on the show. So, absolutely I would go back if it made sense to everybody involved — yes."

Walsh also went on to share how grateful she is by the fans' response surrounding the theories of a likely return, expressing her overwhelming humbleness over their continued love and admiration.

"I also want to take an opportunity to thank the fans, because I know how passionate and loyal they are and I appreciate the all the good will and love for Addison, and of course the whole Grey's family, but it means a lot," she added.

Ahead of the Season 16 premiere, reports surfaced that Grey's showrunner Krista Vernoff was working on securing a big original character's return this year. While she refused to share who that person was at the time, she said talks were happening behind the scenes.

In usual Shondaland fashion, Walsh kept things close to the chest when asked if the character Vernoff was referring to is indeed the beloved neonatal surgeon.

"Oh no, I can't say anything. I couldn't. It's like Shondaland, it's serious business," Walsh told PopCulture.com in a phone interview Thursday, Oct. 16. "I am sworn to secrecy for real."

Addison Montgomery remains one of the most beloved characters in Grey's history. The charade famously led the ABC spinoff series Private Practice for six seasons, making habitual visits to Grey's Anatomy for crossover events. The character was last featured on the ABC medical drama during Season 8's infamous musical episode, when Addison was flown in to help treat Callie's (Sara Ramirez) injuries after a car accident.

Since then Walsh's career has skyrocketed with roles on shows and movies like Girls Trip, 13 Reasons Why, Fargo and The Umbrella Academy. She also has starring roles in upcoming films, including Sell By and 3022 with Omar Epps and Miranda Cosgrove.

The award-winning actress also teased she is working on a "top secret" project at the moment, though she didn't give any more details. Could it be a return to Grey Sloan Memorial? Fans will have to wait to find out!

Along with her busy Hollywood schedule, Walsh was inspired by her dog Rosie to partner up with Zoetis to raise awareness of allergic dog itch. The actress and businesswoman wants to encourage dog owners to recognize when their pets' scratching can be more than just an itch.

The "Show Us Your Dog's A-Game" campaign involves pet owners sharing photos of their own pets living their best lives using the hashtag #MyDogsAGame. Every post triggers a $10 donation by Zoetis Petcare to its K-9 Courage Program, which provides healthcare assistance to retired military and police dogs, along with active service dogs who help veterans suffering from post-traumatic stress disorder.

"[People are] aware of human allergy season, but we also want to bring awareness and attention that dog allergies can manifest in a different way," Walsh said, revealing her veterinarian prescribed Apoquel to Rosie and how it helped soothe the allergy symptoms. "Not necessarily runny eyes or wet eyes... it's usually itching and so with Rosie, she used to do this thing, and I thought it was so cute I would video it and take pictures of her. She'd take both her front paws and scratch her snout at the same time, I was like, 'Oh my God, cute.' And then it wouldn't stop."

"So, I was excited to let people know, like if that's what it's looking like, take it into your vet, see if Apoquel might be right for you, and I just loved Apoquel's campaign, My Dog's A-Game, getting your dog back to their A-game so that they're feeling their best in their joyful, awesome dog state," she added.

Posts that use the hashtag may be featured in an interactive gallery. You can find more information about the campaign, and Zoetis as MyDogsAGame.com. The campaign started in August and will go on until the end of the year.

Grey's Anatomy airs Thursdays at 8 p.m. ET on ABC.