Jennifer Garner's children want to name their new sibling "Donald Duck."

The Butter actress and her husband Ben Affleck are expecting their third child together.

Their daughters, six-year-old Violet and three-year-old Seraphina, have big plans for their baby brother or sister.

"Our girls are working on names," Jennifer told Jay Leno on The Tonight Show Wednesday. "At first they were definitely Disney. It was like, Donald Duck, Minnie Mouse Affleck. And then they've moved on. Then it was Peter Pan, Captain Hook, Smee."

Jennifer was not impressed with the Disney monikers that her daughters compiled. Violet and Seraphina are intent on being involved in the naming process and have adopted other strategies to gain their mother's approval.

"They're coming up with lists, and coming in and saying, Let's have a baby-naming contest! Let's have a baby-naming poll!' " Jennifer gushed. "They ask everyone, cause they just want to know. But we're not telling."

Jennifer knows her baby's gender, but did not want to reveal the sex on the show. Her husband Ben is happy with having a boy or girl, as he will love the child profusely either way.

"I would have thought [Ben wanted a boy]. At first I think I really thought so," Jennifer recalled. "And then he kind of said, Well, we have girls. We know how to do girls. My girls love me. I'm the big guy in the house.' So, now I'm not sure."

Jennifer will be delivering her baby in upcoming months.

Her newest film Butter will be released in US theatres in March.