Hmmm, let's see...
The author has killed off nearly every major character at least once, only to have it turn out that they were never killed.
And
The author keeps using the same 'quest for the magic rock' quest in series after series. (I actually liked the first QFTMR series, but it got old the second or third series out... Then he did prequels...)
And
The author had a book who's main plotline involved a pregnant mummy. (You know, the ones in all the bandages...!) And in another novel had an immortal vampire who could not be destroyed until the end of the world, so when the herroine kills the vampire the world ended! (The only two books that I have ever thrown across the room in my life. After throwing the second one I realized that the rage seemed familiar, so I looked at the spine of the book - sure enough, same author.)
All are different authors.
The Auld Grump