His character had 23 personalities and, in the film, he showed mainly 5 of them, as well as his ‘real’ persona (several others came out as he was unravelling). Each personality was a completely different type of person – 9 year old boy, woman, gay man, OCD man and the BEAST.
When he morphed into the Beast, he morphed into a larger stronger person, proving the doctor’s theory that each personality has a different physiology. The trouble was, the film only really showed this with the Beast, making it a tad ‘unbelievable’, especially when he scaled the walls more adeptly than Spiderman!
For me, as a writer, this film was a huge inspiration for me to tune in more to the voices in my head.
Some actors struggle to pull off one personality, never mind multiple. To play all those different people….well, hats off to you, Mr McAvoy!