From the Book せかいののりもの (“Sekai no Norimono” — Things to ride on of the World), published in Japan 1999, copyright Disney Enterprises Inc. If you look carefully, you can see the characters names in katakana.

So the question is, how intentional is the R — was it a joke — was it deliberate — was it a simple mistake?

The fact that the quality control of Disney products are in general so high makes it unlikely that this is planned: Other aspects of the drawing are done to Disney detail: the colors of the shirts are the traditional ones for the triplets. And such details would not be changed for the Japanese market — Disney sticks with the American versions of character names when written in romaji — see for example Huey Dewey and Louie’s Good Time Cafe at Tokyo Disneyland.

It’s also hard to believe it is a joke. An L / R confusion is a pretty juvenile joke for a talented illustrator, and there isn’t any other running joke or gag that it could be a part of. Not to mention that L / R confusion is a less than flattering stereotype for Japanese. In the picture, the triplets are standing in a road apparently in France ( that’s the double line behind them ), so it is conceivable that there is wordplay on the French ‘rue’, but this seems far-fetched.

So the likeliest explanation is that it was originally a mistake. I doubt we’ll ever know.