After all these years, I still love this song.
Regarding the confusion, there is an image in the Photos section that adds details about who did what, here. For the less french inclined, it goes like this : "it", the posh protagonist of the video, is played by Yves Jacques who is also the songwriter, producer and director of the video.
Pierre Gagnon did not direct the video but was the song's composer and ANOTHER Pierre Gagnon (same name, different person) was part of the band seen in the video, playing guitar. Richard Taschereau was the bassist and Jeff Côté the drummer in there.