Russian Oz

“Russian Oz” was an alter-universal version of the Land of Oz known to the 925th Universe's Doctor Know.

He once stated that he hoped Professor Wogglebug hadn't ventured out into any alternative versions of Oz because the Doctor “still ha[s]n’t taught [him] why he should stay away from Russian Oz”. (PROSE: Annals of the Jen: One Year of Jenny Over-There: Tetra-None Hepta-Oct and Doctor Know-It-All Talk it Out)

Behind the scenes

This is an allusion to the Magic Land series, created by Alexander Volkov in 1939. The first book was a heavily altered localisation of Baum's Wonderful Wizard of Oz, but the subsequent books in the series were wholly original, developing the worldbuilding of their titular Magic Land in quite different directions from Baum's Oz. As a result, a denizen of a more Baum-compliant Oz like Callum Phillpott's would no doubt find it uncanny at best.