Britney Spears may be used to seeing her own face on the cover of magazines - but it looks like the sight of her kids can still stop her in her tracks!

We ran into the pop princess out with Sam, gassing up her car after a quick stop at Starbucks. The pair stepped inside to shop for snacks - when all of a sudden, Britney's eye was caught by Sean Preston adorning the cover of OK! Magazine!

Brit instinctively grabbed a copy of the mag, but didn't get a chance to start thumbing through it before Sam convinced her to put it down and hurry back to the car.

Of course, that was hardly the end of Britney and Sam's adventures at the gas station - they kept doubling back to pick up more snacks! (And hey, why not? Sam told us he owns the joint - surely he's not sweating a spare Fanta or two!)