The musical couple spoke with ET on Wednesday, and despite getting the boot so close to the season finale, the pair said they "had the best time doing the show."
"They had to convince us to do it a little bit," Foster said with a laugh, adding that the ended up having a great time getting to perform in a new and unique environment.
"Got to flex some musical muscles again. Because of COVID, everything had kind of stopped. So this was one of our first musical outings," the iconic music producer shared. "We got to do some great songs and do some stuff we don't normally get to do, and it was a lot of fun."
"Yeah, we really enjoyed it," McPhee added.
During Wednesday's Group B finals, Foster and McPhee kicked things off with a fun, Broadway-worthy rendition of "Singin' in the Rain," which also gave McPhee a chance to show off her tap dancing skills -- and in full costume, no less.
McPhee's versatile performance was met with a standing ovation from the audience and the panel of judges, and impressed Foster as well.
"I was so proud of Kat. She's a triple threat! She sings, she dances, she acts. And she got to do a little bit of all of that," he shared.
"When we watch the show as fans, before we were even on it, I felt like the show was so fun and silly and entertaining. So I wanted to do something sort of silly," McPhee shared. "And no one's really tap danced on the show!"
Performing together -- with Foster as The Banana, often playing the piano, and McPhee as the golden voiced Ice Cream -- the cute couple wowed week after week with splashy productions and incredible numbers that saw McPhee really belt out tunes from a wide range of genres.
"David was behind the scenes... putting his magic on all the arrangements," McPhee said, marveling over the key role her husband played in their success on the show.
"Well, Kat can do any genre of music and do it really well," Foster replied. "So the sky was the limit."
During the episode, the duo also performed a duet with panelist Robin Thicke! Together they delivered a rendition of Stevie Wonder's "Don't Worry 'Bout a Thing" that proved to be a real crowd-pleaser.
However, when it came time to guess who was under the masks, nearly everyone on the panel -- Ken Jeong, Jenny McCarthy and Nicole Scherzinger -- all guessed Foster and McPhee. Everyone, that is, except Thicke. Despite the fact that he performed with them, and that Foster was best friends with Thicke's late father, Alan Thicke.
"I think that's called 'good TV acting,'" McPhee said of Thicke's insistence that his "Uncle David" wouldn't do the show in the first place, so it couldn't be him. "I think he knew exactly who [we] were."
"I held him as a baby, and I truly was best friends with his father," Foster recalled. "He's so much fun on the show."