Dr. Rey -- Big in Prison

9/16/2009 2:41 PM PDT BY TMZ STAFF
"Dr. 90210" has a ton of fans ... at correctional facilities all over the country.

Dr. Rey: Click to watch
Yesterday in Beverly Hills, the good doc Robert Rey read us a letter from incarcerated supporter Rod -- who specifically asked for an 8x10in photo ... which he'll probably hang in his 8x10ft cell.