Taken from the times miners had a Canary down in the mine shafts to detect deadly gasses, this is a check of a toilet after destroying it with your bodily waste to make sure it's clear.

The phenomenon of having to come out as bisexual to the same person/people repeatedly because they assumed or hoped that your sexuality was a "phase." Refers less to the holiday and more to the 1993 Bill Murray comedy film in which the main character experiences the same day over and over.