Clash of the Titans‘ Thursday night shows lured in approximately $4.2 million, setting the Sam Worthington-actioner up for a solid weekend at the box office. Theater chains started screening the film around 8 p.m. last night, with theaters only switching to 3-D for the midnight shows. The movie wasn’t able to topple the 3-D animated flick How to Train Your Dragon, which lured in $5.2 million, but Dragon screened all day long, luring in lots of kids out on spring break. Miley Cyrus’ The Last Song also bested the sword-and-sandal flick with $4.3 million Thursday, putting its two-day gross at $9.4 million. Clash screened on only 500 theaters at 8 pm last night, adding a a few more at 10 pm before getting to its full 3-d run at midnight. Warner Bros. expects Clash’s Friday number to be huge, in the $20 to $25 million range. It will screen in over 3,700 locations, with 1,800 screenings in 3-D.