By Frank Scheck In case you’re wondering about the title of the new feature comedy receiving its world premiere at SXSW, be advised that The Dress Up Gang is an alt-comedy troupe that has attracted a following for their videos and television series. They’ve now parlayed their popularity into their first feature film directed, written by and starring its members. The result is Plantman & Blondie: A Dress Up Gang Film, which is about as wacky as its moniker suggests. Full disclosure: I was previously unaware of the troupe, although several of its members — such as Frankie Quinones, Cory Loykasek and Kirk Fox — are familiar from such television shows as What We Do in the Shadows, Physical and Jury Duty, respectively. What I do know is that this sort of offbeat comic material, best suited for short videos and sketches, can be very difficult to pull off in a feature-length film, as the recent The Napa Boys proved.…