If Iron Man was a jack-in-the-box – a mechanical contraption that turned out to contain a fun, summer-movie surprise – Iron Man 2 is a jack-in-the-box with a bunch more jacks stuffed in (and a few jills for good measure). Only about half of all the new stuff is necessary, but most of it is entertaining. Downey still has charm to spare, while Sam Rockwell, as a rival industrialist, has a blast essentially spoofing Downey’s cocksure attitude. There is also Scarlett Johansson, as a kick-boxing corporate assistant, and Mickey Rourke, cooing to a cockatoo and gurgling in a Russian accent as a physicist gunning for Iron Man.