Why a talking shell? One day, "I was feeling tiny and started doing this voice," says Slate.
Fleischer-Camp, 27, an animator, built Marcel and gave him an eye and shoes. Friends "flipped out" over his debut video.
What are the secrets to Marcel's success? "He kind of tugs at your heart," says Slate. "Kids seem to like that he's so little."
He's small, but sturdy. Marcel lives on the couple's mantle in Brooklyn. If he were on a desert island, he'd need just "a peanut shell for a boat," says Slate, a Twix candy bar – "He could live off one for two years" – and a radio. "He loves Carole King."
For more of the latest book reviews, pick up the new issue of PEOPLE, on newsstands Friday.