There’s something new, something old as “Saturday Night Live” opens its 36th season on Saturday (11:30 p.m., NBC).

• New: Four new cast members, following the sudden departure last month of Mac-Gruber’s Will Forte and first-year casualty, Jenny Slate. The newcomers include Taran Killam (“MADtv,” “Scrubs”), Chicago-based improv comedians Paul Brittain and Vanessa Bayer, and African-American stand-up comedian and impressionist Jay Pharoah. (There are rumors that Fred Armisen’s Barack Obama will be retired, in favour of Pharoah’s impression.)
• Old: Amy Poehler, a former SNL cast member, hosts the opener. A smart move with all the newcomers in the cast. Poehler is expected to join Seth Meyers on “Weekend Update.”
• New: Katy Perry makes her debut as musical guest. She will perform “California Gurls” and “Teenage Dream.” And, with the controversy of her banned Sesame Street video, don’t be surprised to see her in a sketch. Katy’s ready, telling Access Hollywood: “I’m hoping they will let me do a skit. I brought my whipped cream boobs, so if they do a sketch involving like a barista, you know, coffee making, I could be helping people out and stuff like that.”