WMG / Resident Evil: Degeneration

Per wiki policy, Spoilers Off applies here and all spoilers are unmarked. You Have Been Warned.

Leon's pissy-ness in Degeneration is because...

His parasite's removal — In Resident Evil 4, it's stated that the surgery required to get the parasite out can damage the conciousness of the host. Maybe it screwed up his emotional state.

The voice actor, Paul Mercier, was constipated at the time — Proposed by this troper's brother. That would explain why Leon isn't pissy in Darkside Chronicles.

Leon was infected with the Veronica Virus — Javier started releasing spores in Operation: Javier...

He has to face the T and G-viruses again — They caused a lot more trouble than the Las Plagas, and taking down the viruses is his goal.

They ran out of money — After animating Angela's polka-dot dress, they ran out of funds to give Leon different facial expressions so they had Paul Mercier redo all his lines to give the monotone voice to match the only face of Leon they had already created.

Frederic Downing is really Albert Wesker in disguise

He looks a lot like Albert Wesker and he sounds like him to an extent.

Angela's Chronic Hero Syndrome is actually her being Suicidal.

Like Curtis, she was devastated by her Sister-in-Law and Niece being killed in Raccoon, but instead of lashing out at an unfair world, she turned it inwards. Nearly every action she has taken, or wanted to take, would have led to her death, she doesn't really want to be a hero, she wants to die saving someone, like she thought she would have if she was in Raccoon with her family.