The pair worked together to locate the dog belonging to Carax Leos, a director currently working with Driver, 35, on the musical "Annette" in Brussels.
Driver filmed a video asking fans to help him find Carax's dog, Javelot. Carax, 58, owned Javelot's grandfather and father, according to Driver.
"Let's put you in the movie," said Driver. "We'll give you chocolate, we'll baptize your son. We'll do anything to thank you."
Driver is not on social media, but Hamill, 68, is – and he has over 3 million followers.
Hamill posted the video, which received 33,000 likes and nearly 10,000 retweets.
And here is the best part: it worked.
According The Hollywood ReporterJavelot was spotted next to Carax at a train station after the video went viral.
The Driver and Carax movie, also starring Marion Cotillard and Simon Helberg, will focus on a comedian and his opera singer wife. No release dates have been announced.