Bela Lugosi had to fight to be cast in the screen version of Dracula. The studio wanted to cast the legendary Lon Chaney in the role, but his death in 1930 squashed that. They worked up a list of other actors, with Paul Muni at the top and Hungarian immigrant Bela Lugosi way, way at the bottom. Bela was appearing in the stage version of Dracula, and the touring company happened to be in Los Angeles when pre-production began on the film. He worked hard and caught the attention of studio head Carl Laemmle Jr, and history was made.
With Dracula such a big hit, Universal got monster fever, and they began working on adapting a stage version of Mary Shelley's Frankenstein. This being Hollywood, they turned their eyes to the actor who had done so well playing one monster. But Lugosi wasn't interested; in the book the Monster has long soliloquoys, but the stage show had reduced him to a grunting beast. "I was a star in my country," he said. "I won't be a scarecrow in this one!" This was the heyday of the studio system, though, and Lugosi was pretty much at Laemmle's beck and call.
They brought Lugosi in for a screen test. Jack Pierce had not yet created the Monster's iconic flat head look, so they threw a fright wig and some mud on him; the results were a disaster. Laemmle laughed out loud while watching the tests. Lugosi, and the original director, Robert Florey, were kicked off the project.
Things had gotten so far along that there were illustrated ads with Lugosi's name on them, and many in the press didn't believe that Lugosi had left the project. Complicating matters was the fact that the movie didn't credit eventual star Boris Karloff - it stuck with the tradition of the stage show, which credited the Monster as "?" (although the film version does have Karloff's name in the uncharacteristic for the time end credits. In later films Karloff would get star billing, although he would be listed only as KARLOFF). People showed up on opening night in New York City expecting to see Lugosi.
The Lugosi test reel is one of the holy grails of monster fandom. It's almost certainly lost, destroyed by a studio who had no idea these things could be valuable. But who knows - stranger 'lost' items have turned up in the past. The world would certainly be excited if the test footage ever showed up.
Lugosi would eventually play the Monster in Frankenstein Meets the Wolf Man, where he would inadvertantly create the modern image of the Monster shuffling around with his arms outstretched. He only took the part because it was supposed to have lines, but every bit of his dialogue was cut after bad test screenings. That's a story for another spooky day, though.