Rihanna -- Back in the Passenger Seat ... With Chris Brown

RihannaBack in the Passenger Seat... with Chris Brown

And just like that ... Rihanna's back where it all started ...Chris Brown's passenger seat.

The on-again couple relived their past earlier today in L.A., where they picked up some refreshments -- including an Icee -- at a gas station convenience store.

You'll recall, Rihanna was riding shotgun back in 2009 when CB unleashed a ferocious beatdown on her face -- but today, she was nothing but smiles.

Oh yeah, that red sweatshirt she's wearing is Chris' clothing line -- Black Pyramid.

Hope Part 2 works out better.