Duck-tective

Duck-tective is a show that Mabel and Dipper watch at the beginning of "Headhunters." It is a TV show involving a crime-solving sleuth duck, very similar to Sherlock Holmes. The titular duck speaks only through a series of quacks which are translated in the subtitles, though the policeman that he is speaking to seems capable of understanding him at certain points. The animals' limbs move not by choice but by sticks taped to them.

History
Once Duck-tective solves a murder the Constable comments that he's "Really quacked the case." Duck-tective replies with a quack which appears as a subtitle at the bottom translating to "Don't patronize me."

Stan Pines watches it later and calls the duck stupid, despite Duck-tective having just solved the case of the murder. The policeman is heard in "Little Dipper," telling the duck that he's gone too far this time. Mabel thinks of the duck as a genius, whereas Dipper feels he could outwit the Duck-tective and that it's easier for the duck because it's closer to the ground.

In "Mabel's Scrapbook: Heist Movie," it seems the series adapted into a 3D-stereoscopic live-action film, as a poster at the local cinema reads Duck-Tective 3D

In "Soos and the Real Girl," a Duck-tective t-shirt is for sale in Edgy On Purpose in the Gravity Falls Mall.

In "Dungeons, Dungeons, and More Dungeons," it is revealed in the show's season finale that Duck-tective has a twin brother, who had shot him earlier.