The physicist and actor hit it off, and after that initial meeting, they consistently kept in touch. When Charlie Chaplin’s movie titled “City Lights” premiered in 1931, he invited Albert Einstein as a guest of honor. The men arrived donning formal suits and bowties, and photographers and interviewers fussed over them, per The Atlantic. Einstein then went back to Berlin, but even though the two were in different countries, they made it a point to occasionally meet in the United States or Germany whenever one was visiting (via Medium).

In 1933, Einstein went back to the United States, and Chaplin threw an elaborate dinner party for him. According to Mental Floss, the silent film actor wanted Einstein to meet publishing mogul William Randolph Heart, but the dinner quickly became awkward. Einstein wasn’t willing to talk about his scientific theories with non-academics, and Hearst’s mistress allegedly touched Einstein’s hair and asked, “Why don’t you get your hair cut?” It isn’t known whether Chaplin and Einstein were able to maintain their friendship after that dinner.

In 1933, Einstein renounced his German citizenship due to political reasons, and he emigrated to the United States to become a professor. He became an American citizen in 1940.