Felix The Cat was one of the first wildly popular animation series. Created by Otto Messmer and/or Pat Sullivan in April 1, 1919, the series fortified popular animation tropes and helped establish animation as a serious medium.
The shorts were released between 1919 and 1928. Paramount helped produce the first 26 shorts before being passed off to other distribution companies. The shorts were often shown before major motion pictures as a way to lead the audience in. The character was heavily merchandised and became the first cartoon character to become a pop culture icon. The feline originally started out with the nickname "Master Tom" before having his name and style changed to make him more "cute" and appealing.
The shorts slowly fell out of popularity as the sound era came ringing in. Sullivan stubbornly refused to produce sound shorts, a decision that would hurt the shorts more than anything. By the time sound was finally implemented, Disney was dominating the animation industry. Production costs started running so high that by 1929, production had to be halted.
The series was given a very brief revival by Van Buren Studios before fading off into obscurity. In the 1950s the silent shorts were purchased by a television production company that added sound effects to them. Riding high on some minor popularity, the character received several TV shows over the decades, some more popular than others.
A great deal of the original Felix shorts remain missing. Getting an exact number of missing shorts can prove to be quite the chore. Some shorts that weren't even known to have existed have surfaced in recent years. There are also many missing shorts that collectors have claimed to own but have never proven. Some copies of shorts were discarded or misplaced in the past decades. It is also unknown exactly how many later-era Felix shorts have gone missing.
Another interesting Felix-related missing product are the 1928-1938 RCA television experiments. A Felix doll was filmed spinning on a vinyl player and was transmitted on experimental television prototypes. They spent 10 years toning and perfecting the image. Footage from these experiments have never surfaced. People aren't exactly clamoring for its existence, since it's not exactly high-quality art, but it is of historical importance.