Physical (as well as mental) disabilities are challenging, but enjoyable to write, and I am all for these types of characters, which break up the sort of canonical archetype that generally exists. RPs help me practice my own creative writing, and the sort of thinking that has to go behind the altered perspective of a disabled character has forced me to be more fluid and creative than otherwise. What Brovo said sums it up. 

[quote=Brovo]
 it suddenly changes every single line you have to write from that character.
[/quote]

Additionally, physical disability to certain extents (I'm talking about like full-body impairment, displacement, etc) has always been an interesting concept for me to mull over. One of my unused characters has a synthetic body and only retains a human brain and it brings up questions about what constitutes the 'human' or 'soul', etcetera. Neat.