Ludwig Von Drake in Rosa's stories

[lgiver@postoffice.pacbell.net]

On page 4, panel 3, of the "Pied Piper of Duckburg" story, we see Ludwig 
Von Drake in his laboratory in Duckburg (pages 4 through 8 were drawn by 
Rosa).  He looks a lot like Scrooge, but with black eye-brows and 
smaller eyes.   I had forgotten he was in this story, so when I first 
read Rosa's "A Little Something Special", I couldn't figure out who was 
seated next to Gyro's Helper (page 8, big panel 5) that looked like 
Scrooge, except that it couldn't be Scrooge since he was still in his 
money bin.  Wouter explained on DUCK-Hunt discussion that it had to be 
Ludwig Von Drake, and that Don Rosa likes to use him.
    Are there any other cameo appearences of Ludwig in Rosa's stories?
                                        ----Larry Giver