Herbie got his name when the crew of the film was watching one of Buddy Hackett's skits about a ski instructor with a funny accent. Then Hackett said, "If you ain't got a herbie [pronounced hoy-bie], I ain't goin'." The name stuck.
During the exchange between Jim Douglas and Mr. Wu while hanging from Herbie's rear bumper: "Car very strong." "And very fast." "The strength of forty horses." The stock Volkswagen Beetle engine did have forty horsepower.
In the final scene Thorndyke and Havershaw are working for Wu and start spraying each other with lubricant, but the lubricant is black. No new lubricants are black - only used oils become black.
When Jim first buys Herbie, he drives him from a single lane street onto a two lane street and past a sign that says "Left lane must turn left". Jim has just entered a one way street going the wrong way.