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Previews make it look a lot like Big, but it is possible to identify some differences between 13 Going on 30 and the 1988 Tom Hanks film. | Andrew Coffin

Previews make it look a lot like Big, but it is possible to identify some differences between 13 Going on 30 (rated PG-13 for some sexual content and brief drug references), the first starring vehicle for Alias's Jennifer Garner, and the 1988 Tom Hanks film. For one thing, in Big the protagonist was 12. Here, obviously, Ms. Garner's character starts out as a 13-year-old.

More significant to the plot, though, is that the magical transition from child to adult takes place in real time in 13 Going on 30. In other words, rather than a child waking up in an adult's body while everyone else around him stays the same, as in Big, 13 Going on 30's Jenna Rink flashes forward from 1987 to 2004 to inhabit the body of her 30-year-old self.