Premise: The Book That Wrote Itself is a 1999 road movie starring Liam O Mochain, Antoinette Guiney and features cameo appearances from George Clooney, Kenneth Branagh, Melanie Griffith, Bryan Singer, and Chazz Palminteri among others. The film was written and directed by Irish filmmaker Liam O Mochain (W.C.(film)). The film screened at numerous film festivals worldwide and was released in 2000.
Hypothesis: There are additional cameo appearances that remain secret to this day.