In 2006, after almost 80 years, NBC Universal sold all Walt Disney-produced Oswald cartoons, along with the rights to the character himself, back to Disney. In return, Disney released ABC sportscaster Al Michaels from his contract so he could work on NBC's Sunday night NFL football package. However, Universal retained ownership of Oswald cartoons produced for them by Walter Lantz from 1929 to 1943.

Answer this question, if possible (if impossible, reply "unanswerable"): What did Universal retain ownership of from 1923 to 1949?
unanswerable