So imagine if Italy started calling Doitsu-tan nicknames:

Italy: Hey, hey, Doitsu-woof!
Germany: What's with the nicknames all of a sudden?
Italy: Well, I decided to call you some cute nicknames!
Germany: Why?
Italy: Why not?
Germany: ....never mind.
Italy: Ok then, Doitsu-wan-wan, can we go play now?
Germany: I regret my life.