| Description | Character | Type |
| #1 The bald-headed, blue-shirt-wearing leader of the babies. | |
| #2 The younger brother of #1. | |
| #3 The spoiled older cousin of #1 and #2 who can speak with the babies and the adults. | |
| #4 The bespectacled red-haired best friend of #1. | |
| #5 The Japanese-born stepsister of #4. | |
| #6 The close friend and rival of #3 who provides some racial diversity. | |
| #7 The female in the set of twins among the babies. | |
| #8 The male in the set of twins among the babies. | |
| #9 The family pet of #1 and #2. | |
| #10 The Parisian poodle girlfriend of #9. | |
| #11 The mischievous cat of #3. | |
| #12 The first pet of #4, an ill-fated pillbug. | |
| #13 The toy-inventing father of #1 and #2. | |
| #14 The clown-fearing mother of #1 and #2. | |
| #15 The grandfather of #1, #2, and #3, and father of #13 and #16. | |