Credit: John Sciulli/WireImage/Getty Images.

Kristen Bell has a strong emotional attachment to sloths. A very strong emotional attachment.

Appearing Tuesday on "The Ellen DeGeneres Show," Bell recalled how her fiancé, "Parenthood" actor Dax Shephard, surprised her for her 31st birthday last summer by giving her a gift that he said "no one else will ever get in their lifetime." It turned out to be a sloth delivered to their home. The presence of the mammal overwhelmed Bell so much, she says, that she had a panic attack and cried hysterically on her bed. She even proved it by showing video of the moment that was shot by Shepard.

DeGeneres decided to tease Bell by joking that she had a sloth waiting for her backstage. The joke made the "House of Lie" actress tear up, but she otherwise had a sense of humor about it.

Bell stars in the new movie "Big Miracle," opening Friday.