Perfect example was Switzerland. When i got to the episode when he was dancing with Japan (some of the best shit evaaa!) I was like... WTF!!.. but thats because I didn't know him well enough. When I got deeper into the show and I saw the episode again... it was 10000000000 times more funny now that i know how Switzerland is.
Headcanon that one time they dyed their hair and put in contacts and dressed up as eachother and acted like the other, AND NO ONE WAS ABLE TO TELL THE DIFFERENCE (until Italy figured out why "Germany" was being so oddly affectionate and why "Prussia" was giving him death glares the entire time)