How do you spell Fabumouse?

There is no official spelling of "Fabumouse". It appears to be a made-up word, possibly a combination of "fabulous" and "mouse".

If you're looking for a way to spell it, you could use:

* Fabumouse (as you originally wrote it)

* Fabulous Mouse (two separate words)

* Fab-a-mouse (with a hyphen)

Ultimately, the spelling depends on the context and how you want to use the word.