Fly front cabin between YYZ and YOW and you are sure to run into a cabinet minister or three, a gaggle of Senators, and a coven of otherwise unknown MPs. Had Herb Grey sleeping behind me on July 1st flying up to YOW, John Manley down the aisle two week's earlier. Each travels with one or more flunkies (oops, EAs) who also travel front cabin.
As for celebrities, try the YYC-LAX route, again in the front cabin. On my second last MHD I shared a seat [and conversation] with Rob Lowe of WEST WING. Great conversation given the role he plays on that show, and the polling I do, plus past careers I've had in ministerial/deputy ministerial offices in Ottawa. Two weeks later it was Beau Bridge's wife, daughter and mother flying back from a father's day weekend with him in Calgary where he was shooting a feature. Talked to his mother about late husband Lloyd, as we deplaned.