Patrick Dempsey surprised television viewers everywhere last week by returning to Grey's Anatomy. 

We still can't believe we're writing that sentence:

Patrick Dempsey returned to Grey's Anatomy!

Appearing on The Ellen DeGeneres Show, meanwhile, Dempsey offered up a few more tidbits and spoilers in regard to his stunning return.

“I was like, what a great opportunity for people and how great it would be for the fans, really, to see everybody reunited in this sort of bizarre way,” the 54-year-old actor said on Wednesday, November 18.

“And [showrunner Krista Vernoff] came up with this concept where I would come and visit [Meredith] in her COVID dream.”

Wait. What?!?

At the conclusion of the recent season premiere, Meredith was found unconscious.

We were then taken inside of her head and this is when viewers were transported into some sort of beach-based fantasy scene... which concluded with the sighting of her dead husband.

"Derek?" Meredith gasped, just as the episode faded to black.

This, however, is the first time we've heard that Meredith has come down with the coronavirus.

Dempsey played Dr. Derek Shepherd for 11 seasons until his 2015 departure.

He's back now, and not just for a one-off cameo, either.

"I'm not sure how many," Dempsey told DeGeneres on air. "I know I'm throughout this season. He comes back to visit."

According to executive producers, Derek will appear in three more scenes this season.

We also learned that Dempsey's return was kept so secret that not even many of the writers or crew members were aware it was happening until the day of filming.

"We didn't tell the writers for the longest time.

"When she's walking and she looks as someone is calling to her, and she goes, 'Derek?' In the script, I had it as Ellis Grey," Vernoff previously told Variety.

And she goes, 'Mom?'

"We read it at the table that way. Nobody knew what we were doing -- to the point that when the crew showed up on the day we shot the scene, nobody knew. It was top secret."

As for how the idea for his return came about, Dempsey said he reached out to Pompeo to meet up over the summer.

"We were like, 'What can we do to get people to wear masks? How can we make an impact here?'" the actor said on this talk show.

"We hadn't spoken in quite some time. So, we're playing catch-up and she goes, 'What do you think about coming back onto the show?

"'Here's our idea of what we want to do for season 17.'"

Dempsey seemingly left the show under bad circumstances.

But time heals almost all wounds, right?

"I was like, 'What a great opportunity for people and how great it would be for the fans really to see everybody reunited in this sort of bizarre way,'" he told Ellen.

"We were really concerned that someone would take a picture, or it would get out somehow.

"But we managed to keep it a secret, which was pretty phenomenal."

Dempsey says the overall goal here was to help anyone suffering amid the pandemic in whatever way possible.

“There are so many souls that we have lost right now so the idea of having angels around us is very comforting, at least to me,” the actorr told DeGeneres.

As for the response he's received over the past week?

He said it has been "overwhelming and very moving."