It's a pretty well-known fact that Ian McKellen was pretty darn close to portraying Albus Dumbledore, the beloved Hogwarts Headmaster in the Harry Potter franchise, following the death of Richard Harris in 2002.
In an interview with BBC's HARDtalk host Stephen Sackur, McKellen expanded on the story and revealed exactly why he ultimately decided to turn down a part in the film.
“But when they called me up and said would I be interested in being in the Harry Potter films — they didn’t say what part — I worked out what they were thinking, and I couldn’t. I couldn’t take over the part from an actor I’d known didn’t approve of me.”
Yup, according to McKellen, Harris didn't think too highly of him and actors like Kenneth Branagh. Harris thought they were "technically brilliant, but passionless." Ouch.
Ultimately, Michael Gambon portrayed Albus Dumbledore in the remaining films, and McKellen continued his stint as the other huge franchise wizard, Gandalf from The Lord of the Rings.
Now with that squared away, we can all go back to hashing out that age-old Harris vs. Gambon debate.