Rugrats originally revolved around a group of little babies, Tommy Pickles, Chuckie, Phil, and Lil. Tommy's dog, Spike, was also a main character in the series. The little babies are able to communicate with each other through baby speak, although viewers can understand them, because it is 'translated'.
The group is often reluctantly joined by Angelica, the older girl. Angelica is able to communicate and understand language from both the little babies and the adults, which she often uses as an advantage when she wants to manipulate either party. She is usually very mean to the little babies. Susie, who lives across the street from the Pickles, is also able to communicate on the same level as Angelica, though she isn't manipulative. As a result, Angelica and Susie often clash and aren't friends.