Amanda Seyfried's House Adam Brody's Sloppy 2nds

4/17/2011 4:35 AM PDT
Amanda Seyfried is officially crashing in Adam Brody's old pad -- TMZ has learned "The O.C." star owned the giant $1.8 million Hollywood home before Amanda moved in a couple months ago. 

The 9,100 square foot house is located at the bottom of the Hollywood Hills with its own pool and spa -- and it's the perfect place for Amanda's pup ... because it even has its own little DOG RUN.

Mamma mia!