Actor Robin Williams, star of the film "World's Greatest Dad", poses at the film's premiere in Los Angeles, California August 13, 2009. [Agencies]

LOS ANGELES  - Yes, you want to have a great screenplay and a talented director, but no project ever gets made until a star's attached.

You simply can't make a movie without somebody to play the lead and having a star is going to help if you're looking for financing or distribution.

Case in point: "World's Greatest Dad," which opened Friday in New York to a modest $10,300 and comes to California on August 28. Written and directed by Bobcat Goldthwait, it's a thoughtful but outrageous comedy starring Robin Williams as a troubled high school poetry teacher and single parent.

After the accidental death of his insufferably nasty teenage son (Daryl Sabara from "Spy Kids") he suddenly finds himself with the fame and fortune he's always craved. Only question: Can he live with knowing how it came about?

Although the role fits Williams like a glove, it wasn't written with him in mind. In fact, Goldthwait told me, he didn't even plan on asking him to read it.

"Robin and I are old friends and he really liked 'Sleeping Dogs Lie,'" he explained, referring to his 2006 drama that also screened at Sundance. "I really wasn't trying to hit him up to be in the movie."

So what happened? "I was at dinner with him and another friend and I was telling him the new story and he was like, 'Well, can I read it?'"

Moreover, Goldthwait added, "I really wouldn't have written the movie for Robin as a poetry teacher if I had him in mind because I think he covered that pretty well already in 'Dead Poets Society.' So I was really shocked when he wanted to be in it."

On the other hand, poetry be dammed -- this was such a good fit for these two friends. "I think the character is a little bit based on life lessons that Robin and I had to learn as adult men."