Actor Danny DeVito had a very “sunny” birthday Sunday ... “Happy birthday to my favorite (rum) ham,” the actress wrote alongside a photo of the pair of them chomping on ham.

As Frank on the long-running FX comedy It's Always Sunny in Philadelphia ... "Happy birthday to my favorite (rum) ham." Then, she raved about the man who's played him since 2006.

Gabriel Olsen/FilmMagic Rob McElhenney, Kaitlin Olson, Danny DeVito, and Mary Elizabeth Ellis support 'It's Always Sunny In Philadelphia' in 2018 Olson, whose ABC show High Potential debuted this fall ...