You can tell James Dean grew up on a farm

Check out the scene in the planetarium when James Dean lets out a "moo".

---Actually the sound he makes approximates a bull letting out a short bawl ---(as in "Taurus" the bull). It's not a simple and short "Moo" as city kids are taught in children's readers. Its a slightly more stretched out --Mooooo-oohhh. Anyone who grew up around cattle on a farm has heard it many times --especially when a bull has a few cows in heat. He gives a good imitation of a bull. Just like the Indiana farm boy he was.