Hergé: Would I need permission to include Hergé in my novel?

I'm planning on writing a novel about a Belgian kid in the 1930's, who is a huge Tintin fan and goes on a trip to find Hergé.
Do I need to have the rights for such a story?
It isn't my idea to actually write a new Tintin story, but it is about a boy whose life is changed because of the Tintin stories. Although there may be some small references to the original stories in my novel.

Off the top of my head and with the usual disclaimer that this isn't legal advice, I would have thought that you'd be fine. I guess you'd be in the same position as someone writing one of the unauthorised but perfectly legal biographies of Hergé (including a well-renowned comic strip biography in which scenes from Hergé's life are effectively dramatised with a good bit of creative license). Or in the same position of someone writing a book or a movie about an imagined incident in the life of a deceased actual writer (of which I can think of quite a few).
As long as you don't include any real people in your novel who are still alive, I think you should avoid any trouble with libel laws. And as long as you're merely referencing the existence of Tintin books rather than including chunks of their text (or any Tintin images on the cover!) or in any way reworking the plots or characters into your own story, it doesn't sound as if you'd be infringing copyright. But that's just my opinion based on my understanding of what you've said you're planning!

Like Balthazar, I believe that your main concern would be if you refer too directly to the actual Tintin stories in your novel or include an illustration.

The cover would have to have some kind of reference in order to make it stand out. I believe that there are some books of Herge and Tintin which only have a picture of Tintin on the cover but no other photos or illustrations.

As a courtesy you might want to contact Moulinsart, the copyright holders, and ask what their policy is regarding fictional depictions of Herge and if you could include a picture of Tintin on the cover.

Their contact info can be found here.

I think that the advice above is good. I spent many years in book publishing, but I'm an editor, not a lawyer. That said, depicting historical characters in a work of fiction is generally OK, especially if it's not attacking the character (Hergé, in this case) but has the historical person plausibly interacting with the fictional characters.
Asking Moulinsart would be a good courtesy.