He's still in production on the independent film "I Smile Back," with Sarah Silverman.
"It's a low-budget independent film, and a real passion project for all involved," he said. "Sarah's a pal, and I'm excited for people to see her in a new light in this dramatic role."
He's also co-starring in "Bird People," a film set in Paris and directed by Pascale Ferran ("Lady Chatterley").
If it gets accepted at the Cannes Film Festival, Charles says he'll be there to help promote it.
He can also be seen April 15 on "Inside Amy Schumer" on Comedy Central. He plays a manager at a fast-food franchise, and seeing him onscreen with Schumer, you are instantly reminded what a fine comedic actor he is.
"I'm excited by this next chapter for me," Charles said Monday night minutes before his interview with Letterman, which was taped earlier in the day, was about to air.
"Excited, but definitely a little overwhelmed by the intensity of the last 24 hours."