Adventures of Tintin: The Secret of the Unicorn Easter Egg - Book References

In the beginning of the movie the man painting Tintin (and painting him as seen in the books) is the man who wrote the books (the character, not the voice). More obvious is the background, containing paintings of other Tintin characters.
Toward the end of the movie Tintin and company are being chased by a few bad guys. To stop them, Snowy knocks over a crate. That crate has the symbol of (and contains the tins used by) the drug smugglers known as the golden claws, seen in the book The Crab With the Golden Claws, one of the Tintin adventure books.