A flyer for a show at the Horseshoe Tavern gives evidence of a Screamers performance in Toronto on Halloween (see August 6, 2007). Unfortunately, there's no year on the poster, but Imants Krumins who sent me the document attests the show happened in 1978. This event would have been promoted by the 2 Garys (Gary Topp and Gary Cormier) who at the time booked everyone from The Buzzcocks to Talking Heads. The 2 Garys appeared in the film The Last Pogo (1978).
The flyer also features a third Gary, Gary Panter, and his iconic drawing of Tomata du Plenty.