Complex sentence: Who Let the Ghosts Out? is a 2008 horror comedy fantasy film that is based on the book series created by R.L. Stine of "Goosebumps" fame.
Split into simpler sentences: Who Let the Ghosts Out? is a 2008 horror-fantasy film including comedy. That is based on the book series created by R.L. Stine of "Goosebumps" fame.