After successfully skewering Hollywood’s scariest movie (as two of the writers on “Scary Movie”), romantic comedy franchises (“Date Movie”), and Hollywood blockbusters ( “Epic Movie”), writers/directors/producers Jason Friedberg and Aaron Seltzer now set their sights on “300.” The heroic Leonidas, armed with nothing by leather underwear and a cape, leads a ragtag group of 13 – count ‘em, 13! — Spartans to defend their homeland against the invading Persians (whose ranks include Ghost Rider, Rocky Balboa, the Transformers, and a hunchbacked Paris Hilton).