Ashton Kutcher hilariously responded to the pic, writing: "I can't lay on leather shirtless. Too sticky."
Shepard responded: "It was arrogant on my end for sure."
Bell, 39, and Shepard, 44, are also the proud parents of another daughter, 6-year-old Lincoln.
The touching image arrives a little over a week after Bell spoke with ET at Disney's D23 Expo in Anaheim, California, about lending her voice to the much-anticipate sequel to 2013's Frozen, which arrives this fall.
"It's so much fun to sing with those three. I mean, truly," she said of harmonizing with co-stars Josh Gad, Idina Menzel and Jonathan Groff on stage at the presentation. "You don't get to record with your cast mates when you're doing an animated movie, but every time we're together to do press like this and stuff, we are in love with each other."
While on hand, she also teased that the upcoming sequel is going to feature a lot more crooning from Groff, who plays Kristoff the iceman, this time around.
"You are going to get to see Jonathan Groff sing! Really sing! Finally! That was my one critique," Bell said. "We didn't get enough Jonathan Groff singing, and to me, he has one of the best singing voices I've ever heard. I would listen to him singing the alphabet forever, and he really gets his dessert in this movie."
The movie also stars Santino Fontana, Sterling K. Brown and Evan Rachel Wood.