The Percy Jackson franchise trades in hyperactive kids' fantasy, a carbonated alternative to Harry Potter's mug of Horlicks. In the first film, The Lightning Thief, plucky Percy, Poseidon's son (Logan Lerman) bounded off to save Olympus from ruin. In the second, by the blood of Zeus, he's doing the self-same thing all over again; like a wind-up doll, his button eyes gleaming. The kids are charmless, the adults bemused. Anthony Head plays the noble centaur, on hand to help our teenaged protagonists. Stanley Tucci lends support of sorts as a horse's arse.