Mental Floss has a really awesome article up exploring the history of the Animaniacs. Definitely worth a read!
In episode #65, “The Warners 65th Anniversary Special,” we learn that the Warners were created in 1929 to be the sidekicks for Buddy, a real character from the early days of Warner Bros. Animation. Their only role in the Buddy cartoons was to pop out of unexpected places and use giant mallets to make a pancake out of the star. The Warners were soon given their own series of cartoons, but the resulting shorts were considered too incomprehensible for public consumption. The films were locked away in the Warner Bros. vault, and the Warner Brothers were locked inside the water tower at the Warner Bros. studio. Until the present day, when the Warners escaped.