Chuck Jones
I just learned that at one point in the 1950s Warner Bros shut down their animation department. So he called Walt Disney to see, looking for work. He spent four months at Disney and he worked on Sleeping Beauty.
http://www.mouseplanet.com/8944/Chuck_Jones__Four_Months_At_Disney
He received no credit, and didn't contribute anything major but it's still a neat bit of trivia.
"Don't you lay a hand on my sasquatch!"share