YOU SAID:

my cat is really a dog in disguise

INTO JAPANESE

私の猫は本当に不幸中の幸い犬です。

BACK INTO ENGLISH

My cat is very fortunately dog.

INTO JAPANESE

私の猫は非常に幸いなことに犬です。

BACK INTO ENGLISH

My cat is very fortunately the dog.

INTO JAPANESE

私の猫は非常に幸いなことに、犬です。

BACK INTO ENGLISH

My cat is very fortunately the dog.