Photography by: Splash News Online

JUSTIN BIEBER’s just like his Calabasas mansion: Pretty on the outside -- a foul, stinking mess inside!

Dwieber’s $6.5 million pad “looks like a frat dorm from the movie ‘Animal House,’” said My SpyWitness, who’s visited often. “Only Justin’s bedroom and one other small room have any type of furniture. 

The rest of the house is filthy!

 Floors in the main rooms are littered with countless candy wrappers, smelly scraps in bags from fast food joints, dirty cups and plates – and dingy clothes belonging to his hangers-on, who camp out and crash on soiled pillows and comforters strewn everywhere.

His housekeepers just can’t keep up with the constant mess and garbage. 

Justin’s always impeccably groomed, so I was really shocked when I saw what a pigsty he lives in!” OINK!