One of the Canadian firefighters accepts the apology from Mouch and Otis on behalf of "the Commonwealth of Canada". Although Canada is part of the British Commonwealth of countries, the country itself is not a "commonwealth," and no citizen would refer to it as such. It was formerly officially a "Dominion," and though this is no longer technically accurate, it generally would not be unusual to say "The Dominion of Canada."
One of the Canadian firefighters says "lieutenant" with the US pronunciation ('LOO-tennant'). In Canada the word is pronounced 'LEF-tennant' (as in most British commonwealth countries).
Talking about a prior prank of putting hot sauce in a hamburger, Otis says he got it from Dumb and Dumber (1994). In that film, the characters put hot peppers on a burger another character was eating, not hot sauce.