Actor-comedian David Spade had a productive birthday weekend around Boston. On Friday night, he surprised fans by joining the lineup at the Comedy Studio in Harvard Square. He performed for about 20 minutes and posed with staff from the Hong Kong restaurant downstairs. On Saturday, he had dinner with actor Alexander Ludwig , of “The Hunger Games,” who plays Spade’s son in the local movie “Grown Ups 2” (the two fake relatives also went to one of the Aerosmith shows together last week). Spade’s real birthday was Sunday. He turned 48.