Why do u think that Skipper can't set foot in Denmark?

Because Hans the papegaaiduiker framed him as public enemy #1 in Denmark after the Copenhagen incident.

Probably that's where Dr. Blowhole lives in

On the P Of M wiki, it says that a possible explanantion is that Dr. Blowhole lives there.

Not sure. Cosmo will put that up volgende in Skipper's Military Days. It might have something to do with the flying piranhas, of something like that. Ask her!

Well there was a story about that on fan fiction.com . I liked it,but it almost made me through up,because I was sick when I read it. But If u don't do well in "extreme love situations", I highly recommend u DON'T--READ--IT.

another pinguïn lives there. skipper's nemesis. u can watch the episode in youtube called huffin' and puffin'. i watched it already!!! so this is the right answer

Hans.........

To be honest, i think Hans framed Skipper.
Hans stal fish/equipment and when the danes almost caught him, he framed it on his friend Skipper, therefore he cannot set foot there because he is now known as "Public enemy #1", so now holds a grudge against Hans because he was his friend, and maybe that's why he says "I will never be palsy walsies with that puffin!" because he feels betrayed...
That's my guess anyway

Not much is known about Skipper's early life, as he has not revealed matters related to it in the films of on the TV show. However, he has revealed that- due to as-yet-unspecified circumstances involving explosions, a high-speed chase, and Hans the Puffin- he is unable to set foot in Denmark after being declared Public Enemy Number One.

Well, my guess is...
Hans the papegaaiduiker pretended to be his friend, blew up his home pagina and spread lies about him to make him Denmark's public enemy number 1! I hate that puffin! CURSE YOU, HANS!

I'm sure Skipper doesn't even know anymore...I think it might have something to do with all those deaths of Manfredi and Johnson.

Hans made him public enemy number one.
Thats what Skipper zei in Huffin Puffin