Well... All of them
The only one I can't recognize is the red bird with a captain hat, but I think that it was created for this intro. He doesn't look like a character from the books.
Most, if not all of the "new" characters in the opening were created by Romano Scarpa, who is - more or less - Floyd Gottfredson's/Carl Bark's heir together with Don Rosa, and probably the most influential Disney artist/writer in Italy. He created literally dozens of characters which are still used nowadays.
I am focusing mostly on Italian Disney because it's the company I know the best, and I am pretty sure that there are similar examples around the world which I don't know that well, or I don't know at all. However, I seriously think that it could be one of the most successful, if not THE most successful comic book company I have ever seen in terms of creative use of pre-existing characters. Since the 1960s they have published literally thousands of stories, and they have worked on these characters for such a long time that they successfully expanded the Disney universe in every possible creative direction. There have been stories about EVERYTHING. There are stories about Donald's superhero identity, stories about secondary characters like Gyro Gearloose and stories about super-secondary characters like Gyro Gearloose's uncouth neighbor. There have been cyberpunk stories about Mickey, hard sci-fi stories about Donald, hardboiled Mickey adventures, vintage stories (taking place in the 1930s) about Goofy and even Sex and the City-style stories about the duck girls from Duckburg. Continuity is VERY loose, but the quality has generally been very high (with some drops here and there). I am somehow sorry that right now I am too old to enjoy this stuff as much as when I was a kid
Some badass Mickey/Donald images:
https://www.fumetto-online.it/ew/ew_...K-GIANT047.jpg
https://images-na.ssl-images-amazon....1DySMxc5AL.jpg
https://www.dcleaguers.it/wp-content...over_mm-03.jpg
https://pbs.twimg.com/media/C4p2S_aWIAACgZi.jpg