First off, we aren't talking knickers, lads - this is the true-blue USA and the pants in question are denim trousers. These amazing jeans magically fit each of four friends: rebellious Tibby (Amber Tamblyn); curvy Carmen (America Ferrera); prissy Lena (Alexis Bledel) and sporty Bridget (Blake Lively) - who are spending a summer apart for the first time ever.
The stuff that 10-year-old girls' dreams are made of is packed into the two-hour run-time: dreamy boys, caring families, friends 'til the end. But the sly, slick cutting quickly loses momentum, allowing formula to take over - all sass gone, you're left wading through a pool of syrup towards the motorway-signed ending.
It's Ferrera who's the molten core in the middle of all this messy meltdown; her spark-spitting Carmen holding the centre while all else is being shaken loose. Your tweenage sis is gonna love this. Unfortunately, you won't.