So far, Sue has dubbed a wheelchair-bound glee-club member a "cripple," isolated minority students from the white kids, and promised to give Morrison's character a kitten and then punch him in the face.
"That's what I love about Sue. There's always that dark person inside of us. That little devil on our shoulder, whispering in our ear," she said. "There are awful thoughts going through my mind at all times. And Sue says them."
Lynch said she's not quite as callous as her character -- at least not in public -- but she does have a certain edge that she can lend to Sue.
"I'm not as mean, but I can be sharp if pushed," she said.
Her favorite Sue insults? Anything having to do with Morrison's perfectly coiffed curls.
"I love when I get to make fun of Matt's hair," she said. "[Show creator] Ryan Murphy is obsessed with Matt's hair."
The two actors, at their best going head to head in the principal's office, said they often feed off each other and have at times, veered off script only to have their improv version make it on the screen.
"Jane Lynch is my new comic icon," Morrison said. "Getting the chance to work with her -- she's really raised the bar for myself as an actor."
But Lynch insists that most of Sue's poisonous lines come from the writers.
"They are from the sick twisted minds of those gentlemen," she said. "I think it comes from their inner mean girl."
Morrison said he's relishing his first leading role on television after years of racking up accolades, including a Tony nomination, on stage.
"I've been trying to make a break into the TV and film world for probably about six or seven years now," Morrison said, admitting he was skeptical about taking the role of Will Schuester, given the historically rocky track record of musical television.
But the response, he said, has been "overwhelming."
"It's changed my life," he said.
After all, where else on television could a stage actor get the chance to freestyle to Young MC's "Bust a Move?"
And working with a cast of young, relative unknowns who are just cutting their teeth in the business has only helped the production, he said, instead of hindering it.
"There's no diva-ness," he said. "They say jump and the kids do it."
A one-time high school performer himself -- his high school glee club once performed "Tiny Bubbles" with Don Ho in Hawaii -- Morrison said his Will Schuester comes from his own glee club leader, but also his high school English teacher.
"I don't remember him teaching me where to put a comma … but he taught in the moment," he said. "It wasn't a job for him."
Mr. Schuester has faced some criticism from viewers, most notably for being so dense as to not realize that his wife, played by Jessalyn Gilsig, has been faking her pregnancy for months, all the while scheming to adopt the head cheerleader's unborn child behind his back.
So how can Mr. Shue -- who seems so in tune and all-knowing at school -- be such a simpleton at home?
Morrison realizes that part of his character can come off a little stupid onscreen, but defended him as a man who just "really wants a family."
Careful not to reveal any plot twists, Morrison promised something big for "Glee" fans.
"Relationships are constantly changing. "Some sh-- is going to go down," he said. "Everytime I read a script. I can't believe it."