There is a particular action that has become the test for whether an actress can 'do' broad comedy: the Julia Roberts Manoeuvre - that random slapstick tumble that proves the glamorous heroine is just an ordinary gal. Roberts is the queen of it (although she nicked it off Katharine Hepburn), Cameron Diaz could do it to Olympics-standard, but Jennifer Lopez makes it look unnatural. And, let's be frank, it's been a while since Roberts herself showed an aptitude for looking foolish. Well, Jennifer Garner is the JRM's new poster girl.
As the soft centre of this lady-shaped Big, she exhibits an egoless comic ability that nobody ever had reason to suspect from her time playing the shrink-wrapped action heroine of spy series Alias. She also possesses a guileless charm that makes even the most ludicrous plot point seem plausible, from time-altering magic dust to the idea that 13 year-olds can run magazines (only partly true).
The romantic plot itself is textbook: Jenna quickly realises that scruffy childhood friend Matt is a much better match than her pert-pecced beau, but (gasp) Matt has a girfriend. Yet it resolves the obstacles in unpredictable ways, with a girlfriend who's not a hateful bitch, a leading man who's actually not head-over-heels for the leading lady and an ending that flirts with tear-jerking tragedy.
And even if some of it is a bit thin - the parallel plot that sees Jenna putting her ailing magazine back on track is naive - the pace and jollity are maintained thanks to playful direction and a cast whose mismatched parts make a satisfying whole. Ruffalo is far more charming than the usual love interest with his embarrassed scruffiness, and Andy Serkis, in his first major post-Gollum role, is a constant hoot as Jenna's fey publisher.
If there's a criticism to be made, it's that the script doesn't push itself far enough with the moments in which it excels. The time-travel element, the film's major change from the Tom Hanks vehicle that clearly inspired it, allows for some great throwaway jokes - mobile phones are a mystery, Eminem is peanut or plain - but it gives up on this successful angle after a triumphant dance rendition of Michael Jackson's Thriller. A few more jokes skewed towards those aged 30 rather than 13 could have secured crossover success.
