Buster Keaton: A Filmmaker's Life by James Curtis:
Keaton resolved to do the best he could with Her Cardboard Lover because an infinitely better picture was in the offing, one that could help him break out of the rut of progressively worse comedies. Thalberg and producer Paul Bern were assembling an all-star cast for the movie version of Vicki Baum’s Grand Hotel, and director Edmund Goulding thought Keaton would make inspired casting for the role of Otto Kringelein, an aging German bookkeeper with only weeks to live.
“In almost every picture I’ve made,” Keaton told Goulding, “I make it a rule to become very serious about the fourth reel or so. That is to make absolutely sure that the audience will really care about what happens to me in the rest of the picture.” Thalberg, especially, knew what a good actor Keaton could be, and multiple tests were made that stretched into the early days of Her Cardboard Lover. Keaton was so pleased he drove home one night in his costume and makeup, bedeviling Jimmy and Bobby, neither of whom could tell it was him. With his heart set on playing the role, he nonetheless knew there was very real concern that audiences conditioned to laugh at him might wreck the picture, something that had happened the previous year to comedienne ZaSu Pitts, who had to be replaced as Paul Bäumer’s dying mother in All Quiet on the Western Front after an unruly preview in San Bernardino.