Quentin Tarantino’s new film Once Upon a Time in Hollywood presents a unique sort of release scenario. There are only three main characters in the film, but all three are played by the biggest movie stars in the world—you’re not going to see Leonardo DiCaprio or Brad Pitt going all-out to do press. The same goes for Tarantino, who’s a star in his own right, which means interviews are few and far between.

So that’s why it’s a delight to see DiCaprio and Tarantino sat down for a 14-minute deep-dive into the character of Rick Dalton. For those unaware, Once Upon a Time in Hollywood takes place in 1969 and finds DiCaprio playing a semi-famous Western TV star who hasn’t been able to break into movies. In the video below, Tarantino and DiCaprio go in-depth about the inspiration behind the character of Rick Dalton, how the character evolved once DiCaprio signed on, and Tarantino even gives a very detailed backstory for the character.

Perhaps most surprisingly, the two reveal that Dalton suffers from undiagnosed bipolar disorder. The character trait was inspired by 70s actor Pete Duel, who was the star of the Western TV series Alias Smith and Jones before committing suicide in the middle of the show's run. Tarantino says in doing his research, he discovered Duel suffered from undiagnosed bipolar disorder, and once he and DiCaprio got to talking, it made sense to them that Dalton would likely be suffering from a similar condition for which he’s self-medicating—hence the heavy drinking.

The whole video is utterly fascinating, and makes me yearn for a feature-length audio commentary on the film with Tarantino, Pitt, DiCaprio, and Margot Robbie. Alas, that’s unlikely given the lack of commentary tracks on Tarantino’s other home video releases, so a feature like this is the best we can hope for.