Gunn's first major Hollywood screenplay was Scooby-Doo in 2002. In 2004, he wrote the screenplays for the remake of Dawn of the Dead and the sequel Scooby-Doo 2: Monsters Unleashed. With these films, Gunn became the first screenwriter to have two films top the box office in consecutive weeks. That same year, he executive produced and starred in the mockumentary LolliLove, directed by and starring his then-wife Jenna Fischer. His film directorial debut was the 2006 horror-comedy Slither, which was included on Rotten Tomatoes' list of the 50 Best Ever Reviewed Horror Movies.
Gunn's next projects included the comedy short film 'Humanzee!' which was originally intended exclusively for the Xbox Live's Horror Meets Comedy series of short comedy films by horror directors, it was replaced with 'Sparky and Mikaela' which debuted on Xbox Live on December 31, 2008.
