Some productions have additional characters, like Noilly Prat in the World Tour, in order to strengthen the cast. But this is very rare.
In other productions like in London, swings were sometimes on stage as "nameless cats". By looking on the brochure, I have identified 3-4 different "nameless toms" in London and UK Tours. One of them was called "George Bailey" as his costume looks like a mixture between George and Bill Bailey.
In all productions, we can see at the beginning of the shows three toms called "Young Old Deuteronomy", "Young Gus" and "Young Tugger". They are played by the artists playing Old Deuteronomy, Asparagus/Bustopher Jones/Growltiger and Rum Tum Tugger. Their make-up and costumes are lighter than the ones from their character, they look like ordinary cats. For example, "Young Tugger" has a classical size of wig instead of the big Tugger one.
 
 
Young Gus, Berlin 2002 - Jeff Shankley

 
Young Old Deuteronomy, Madrid 2003 - Pedro Ruy-Blas

 
Young Tugger, US Tour IV 1987 - Steven Bland

 
Nameless tom 2, London May 1993 - ?

 
Nameless tom 1, London 1996 - ?