"When we wrote the song, immediately you start thinking of video ideas in your head. The whole concept of the song is this little girl hears her parents fighting and it really affects her," says Underwood, 31.
"There's so many people who can relate to a story like that. Talking about words and how much they can hurt and you just wish they were more like little playthings, things that didn't actually do any damage.
"Basically we were like what do we do with this?" she says. "I didn't want to follow the storyline exactly and I didn't want it to be too serious, I just really wanted it to be relatable."
So she called in P.R. Brown, the director of her "Two Black Cadillacs" video, who came up with a storybook theme where the little girl gets to be the hero.
Underwood immediately knew just the perfect little girl to play the tiny heroine: Grace Rundhaug, 8, who played Marta in last year's The Sound of Music Live!
"Whenever I thought of the types of things I wanted to see in this video, I just saw her face," says Underwood. "She'd be the perfect little girl in the song and in the video."
Go behind-the-scenes on the "Little Toy Guns" shoot in the clip above.