I am sorry... yes, he/they were dog(s). But is the movie not called Rin-Tin-Tin?
I don't think it's right that the two dogs that played Rin-Tin-Tin in this movie--Rin-Tin-Tin II and Rin-Tin-Tin IV--would make the so-called 'complete' list of cast COMPLETE.
Hey, guy, when you see a movie about Christopher Columbus, do you expect the real person or the actor?
You do have a point though about what dogs they used. Rin-Tin-Tin died in '32 at the age of 14. I don't think any dog in this 1954 show could rightly be called Rin-Tin-Tin II.
Just think, by now they would probably be up to Rin Tin Tin Ten.
It ain't easy being green, or anything else, other than to be me