The actress pretended to be an audience member on "The Ellen DeGeneres Show" during an "Ask Dr. Dax" agony uncle segment on the programme, which taped on the "CHiPs" star's birthday on Wednesday, January 02.
Bell asked her man if there was a gift she could get a special someone, "like a spouse", on his birthday and was left a little misty eyed by her husband's response.
"In the bedroom?" he asked mischievously after previously helping a real audience member with advice about how to get the most out of sex, prompting Bell to state, "Let's say I have 'in the bedroom' covered!"
Dax, who was wearing overalls decorated with photos of his hero, Brad Pitt, then floored his wife by saying, "I would say, 'Please please please give that person love and support for 11 years, give them two beautiful baby girls and you're good'."
Visibly moved by his answer, Kristen pointed at her husband and said, "You're crying too!".
"You sit down, young lady," Dax responded. "We've heard enough of your question."
Kristen then joined her man onstage for a hug and a kiss before the couple was led over to a birthday cake by host Ellen DeGeneres. A man dressed as a clown popped out of the cake as the trio approached.
Bell shrieked as Dax, who has appeared regularly on the show over the past year to host his "Ask Dr. Dax" segment, during which he answers audience members' awkward sex and personal questions, confessed he had a hunch there was someone in his cake as he approached, but added it was the "perfect" birthday surprise.