Look after your brother, ya idjit.
"Idjit" is an affectionate, but exasperated, appellation applied by Bobby to Sam and Dean - first heard in 3.03 Bad Day At Black Rock. It has become something of a catch phrase, and Bobby's use of it is imitated by Crowley in 6.04 Weekend At Bobby's.
In 7.10 Death's Door, Bobby's dying word to the boys is "Idjits".
Jim Beaver refers to the followers of his Twitter as "Twidjits".