Assorted headcanons about Alan Smithee/Show Runner:
They like horror movies a lot; their BTAS incarnation is partial to classic-style monster movies and murder mysteries, while their 2004 version is more fond of 90s/2000s era slashers.
They have a gun that's designed to look like an old timey film camera. The bullets are stored in the reels where the film usually goes.
The straw that broke the camel's back and officially led to their start of darkness was when they submitted a film to a local film festival. It was a surrealist horror movie that had a lot of deep personal meaning to them, and when it became a laughing stock among the public at large, they felt so deeply angered at the fact people would mock their pain so frivolously.
They have a deep appreciation for all kinds of art, not just film and theatre.
In regards to their relationship with Oswald: they never hesitate to tell him how beautiful they think he is. They often refer to Ozzie affectionately as "pretty bird."
Alan likes showing Oswald affection by kissing him on his nose and flipper hands, as well as stroking his hair. Not to mention general hugging cuz he's extremely huggable.
In BTAS, Alan believes Oswald has a beautiful singing voice and has encouraged him to perform at karaoke nights over at the Stacked Deck.
Alan connected with Oswald because they too know how it feels to be rejected by society, and not just cuz of the incident with their film; as an autistic person who's filtered their perspective on life and communication through their special interest (movies and TV), it's been hard for them to get by in society as well. (Not to mention I headcanon Oswald as also being autistic so ya know, there's that.)
They also have a friendship with the Ventriloquist, appreciating his namesake talent. In the 2004 continuity, they were a huge fan of Cockamamie Junction as a child, and are sad to see him fall on such hard times as of late.
They have no particular hatred for Batman, far from it, actually; in their goal to keep the reputation of Gotham alive and thriving, they typically expect Batman to come foiling their plans and take it in stride most of the time. That said, they do wish they could win for once sometimes.
They're sometimes accompanied by henchmen themed after other members of a film crew, like boom mic operators, makeup and costume artists, caterers, etc.
They do still want to work legitimately in showbiz despite it all, but after that initial attempt at trying to break through, they just don't know if they're really cut out for it. They continue to write scripts and try to score small gigs on actual film sets from time to time, but they have trouble going beyond that due to the fear of yet again being perceived as, well, cringe.