Do writers use pseudonyms to write "crossover" books?

Surprisingly, I've never heard of this in the book publishing world.<br><br>In the music world, famous artists have been writing music for sometimes similarly-themed artists and sometimes quite differently-themed artists for many years. For example, one of my favorite pop artists, Max Martin, has written a good number of Disney soundtracks while simultaneously writing chart-topping pop songs for people like Katy Perry and Justin Bieber.<br><br>I can't think of a single example of where a famous author has written a children's book or fantasy novel under a pseudonym.<br><br>Was thinking of authors like Stephen King or Dean Koontz.