Prussia/Canada, sometimes refered to as PruCan (made by combining the names Prussia and Canada) is a pairing involving the characters of Prussia and Canada. It is popular in Fanfictions and Devianart.
The only actual interaction the two had was when Prussia hacked Kitayume and made it his blog during April Fools '09. Canada arrived, claiming that "Maple syrup surely brings happiness to the people who eat it", and gave Prussia, who was skeptical, a bottle for free. After tasting the syrup, Prussia stated that he enjoyed it.
It should also be noted that Prussia actually remembered Canada, and never mistook him for America.
Fan Speculations
Some fans like this pairing because they are both sometimes referred to as loners. Prussia being lonely (despite saying "It's so fun being alone" all the time) and Canada rarely being noticed is a large factor in foundation of the pairing.
Fans also like to use the link of New Prussia in Wilmot Township, Waterloo Region, Ontario, Canada as a platform for theories and fan-material.
Additionally, many of the remaining speakers of Low Prussian (commonly referred to as simply Prussian) currently reside in Canada.