[1] Born in Ottawa, Ontario, Mosher attended fourteen different schools in Montreal, Toronto and Quebec City, graduating from the École des Beaux-arts in 1967.

He famously won entrance to this fine arts college (now part of UQAM) by forging his high-school graduation certificate, which he called his most successful work.

[2] During his summers as a student, Mosher started drawing cartoons, "portraits of American tourists" on the cobbled stone streets of Quebec City.

[3] He has admitted that he knew little about his chosen trade, and the lack of historical books about Canadian political cartooning made the transition a challenge.

[6] In the fall of 1970, Montreal found itself in the middle of what is known as the October Crisis, in which the pro-sovereigntist group Front de libération du Québec (FLQ) kidnapped and killed Pierre Laporte, a senior Quebec cabinet minister.

[6] The Federal Government, led by Pierre Trudeau, invoked the War Measures Act, thereby suspending civil rights and liberties.

[10] Mosher and fellow Montreal cartoonist Serge Chapleau were the subject of a 2003 documentary film, Nothing Sacred, directed by Garry Beitel.

[13] Mosher has had a long association with the Old Brewery Mission, Montreal's largest shelter for the homeless, and in 2001, was appointed to the institution's board of directors.

[17] In 1993, MP Robert Layton denounced Aislan's cartoon depicting outgoing Prime Minister Brian Mulroney lying face down in the snow after having been tripped by a whistling Pierre Trudeau[18] as "a crime against fundamental Canadian values of decency and mutual respect", making him the first political cartoonist censured in the House of Commons.

The cartoon was drawn in reference to a Montreal Muslim woman who refused to remove her niqab upon entering a French-language school and was asked to leave.

[20] Salem Elmenyawi, the president of the Muslim Council of Montreal, pointed out that he had made similar cartoons about women wearing a hijab.

[21] Elmenyawi explained that the cartoon creates an inaccurate depiction of women who wear niqabs by "not respecting the fact they tried to be true to the faith the way they understood it and the way they think it's right.