One idea could be France taking on the role of a mentor to baby Canada. He could teach Canada about art, cooking, and the French language. Another plot could involve France trying to protect baby Canada from the chaos of the Hetalia world. Maybe some other countries misunderstand Canada's relationship with France and France has to clear things up.
At first, it might be a bit of a one - sided relationship where France is very enthusiastic about baby Canada. France would probably dote on baby Canada, showing him all the wonderful things about France. As baby Canada grows, he might start to become more independent but still have a soft spot for France. He might learn to appreciate France's culture while also asserting his own Canadian identity.
France would be a likely candidate. France has always had a sort of motherly - like affection for Canada. He would probably be very eager to take care of baby Canada, dressing him up in cute clothes and feeding him French cuisine, like crepes.
One common theme is brotherly love. Since America and Canada are siblings in Hetalia, in these baby - themed fanfictions, they often show a pure form of brotherly affection.
I recall a fanfiction that focuses on the relationship between their guardians and Baby America and Canada. It shows how the two little ones grow up under different influences. The story is filled with both humorous and touching scenes, like when Baby America tries to imitate the grown - ups and Baby Canada is just there being his calm and observant self.
Well, perhaps in the fanfiction, Canada turns into a baby due to some magical mishap. The nations have to search for a way to turn him back. Meanwhile, baby Canada is just exploring the world around him innocently. He might crawl over to England's tea set and accidentally break a cup, leading to England's typical over - reaction.
It might be about Canada in the Hetalia universe going through a sudden change, like snapping. Fanfictions in the Hetalia fandom often take the existing personalities of the characters and push them in new directions. So this could be about Canada breaking free from his usual shy and reserved self and doing something unexpected, perhaps standing up to the more dominant nations in a bold way.
One common theme is the other nations' concern or lack thereof. Since Canada is often overlooked, sometimes the other characters are slow to realize he's sick. Another theme is Canada's own struggle with his illness in solitude. He might be used to taking care of himself and not wanting to bother others.
Family is a common theme. Since America and Canada are often depicted as brothers in Hetalia, fanfictions explore their sibling relationship, like how they argue and make up.