Return to Oz is a 1985 film which is an unofficial sequel to Victor Fleming's The Wizard of Oz. The film is based on the second and third Oz books, The Marvelous Land of Oz (1904) and Ozma of Oz (1907). The element about Tik-Tok being "The Royal Army of Oz" derives from Tik-Tok of Oz (1914), in which he is made the Royal Army of Oogaboo, and also makes frequent cries of "Pick me up!" That book was itself based on a dramatic production, The Tik-Tok Man of Oz (1913).

It was made by Walt Disney Pictures without the involvement of MGM, the studio that made the 1939 film. No approval was necessary, because by 1985, the Oz books on which the film was based were in the public domain, and the subsequent Oz books had been optioned to Disney many years earlier. A large fee was paid, however, to use the ruby slippers, which were still the intellectual property of MGM at the time (the rights to the 1939 film and all elements now rest with Time Warner). The film was directed by Walter Murch, a respected editor and sound designer. Although it did not fare well at the box office and received mixed reviews from critics it has gained a loyal following.

There was a sequel to Wizard of Oz?

I'm not so sure if it is a sequel. I would call it more of a retelling of the story. You could very well consider it a sequel though.