The former “American Idol” standout made it a point to poke some fun at the pair’s age gap in response to a fan who mentioned how McPhee was absent from the 16-time Grammy-winning Foster’s 1992 Christmas album.
“Am I playing #DavidFoster 's 1992 xmas album for my entire office? Yes. Do I have no shame? Yes. The only downside is no @katharinemcphee on this album,” one Twitter user wrote, tagging McPhee in the post.
The 35-year-old singer took the joke in spirit and issued her own sharp commentary.
“The recording schedule for this conflicted with my 3rd grade homework, unfortunately,” McPhee bantered, spurring a slew of memes praising the “Waitress” Broadway performer for her witty remark.
The pair has previously defended their age difference with McPhee calling their love “genuine,” adding that they “respect each other and have for a very long time.”
“There are just a lot of things when you look at the history of our relationship, neither of us could have written it,” she told People in September 2018. “I would never have imagined that this would be our future together.”
“We understand each other,” Foster, 70, said.
“He has things to learn from me and I have a lot of things to learn from him. So I think we have a nice yin and yang," McPhee concluded. “It doesn’t make sense to a lot of people, but it does to us."
McPhee and Foster tied the knot at a church in London this past June. The couple first met in 2006 when McPhee was a contestant on season 5 of "American Idol" and Foster was a mentor on the singing competition series.
Foster proposed to his bride in July 2017 with a huge emerald diamond ring while the couple was on vacation in Italy. For her very special day, McPhee wore a custom-designed strapless gown by American designer Zac Posen. It featured layers of tulle, a sweetheart neckline and a matching veil.
This marriage marks Foster's fifth and McPhee's second.
Fox News’ Jessica Napoli contributed to this report.