In Sandman Vol 5: "A Game of You", Wanda dreams of Weirdzos which are the same as Bizarros from Superman lore.
Indeed this site notes a misprint:
The word “Bizarro” that had accidentally appeared in Sandman #32, has been changed back to “Weirdzo”. (DC had nixed the use of the word “Bizarro” and “Weirdzo” was used instead. When #32 was printed, one of the “Weirdzo”s had fallen off revealing the “Bizarro” underneath.)
and a comment on this site says:
As an old Superman fan, I quickly figured out who Weirdzo and Lila were; obviously, Bizarro and Lois Lane. But this is a DC imprint; why couldn’t the real ones be used? Well…, I guess DC didn’t like the idea, somehow.
This question and answer, seems to note that it was Gaiman's choice to stop using heroes, but that doesn't quite gel with the misprint noted above in this case.
I haven't been able to find why DC apparently didn't want Bizarro being used. I am assuming that it was down to a Vertigo / Mature Readers imprint vs normal DCU issue, but can't find for sure.
Does anyone know the full story here?