You know you’ve made it as a voice actor when hordes of fans are uploading impressions of your roles. So it is with Tom Kenny, who is best known as the voice of Spongebob Squarepants, and has lent his distinctive tones to many other animated characters besides.

In a video for Vanity Fair, Kenny reacts to fans’ takes on his characters, such as Spongebob, Heffer (Rocko’s Modern Life), the Ice King (Adventure Time), and the Mayor of Townsville (The Powerpuff Girls). As he reviews their performances, he gives unprecedented insight into his own approach to voice acting. His advice can be broadly summarized as follows:

Be versatile. Under union rules, says Kenny, an actor can be contracted to voice up to three characters on a tv series without a pay rise. Producers “would rather pay one guy to do three voices than three guys,” so make sure you can do three.

Talk to yourself. It’s a good way to practice your voices.

Imitate others. “A lot of times, voices are amalgams of half-baked impressions,” says Kenny. His influences include his teenage nephew, the Wizard of Oz, and Ruth Gordon in Every Which Way but Loose.

Go big on the emotion. “I tend to play a lot of characters without any filter,” says Kenny. In the video, he delves into the psychology of his characters, highlighting each one’s defining trait: Heffer’s joy, the Ice King’s loneliness, etc. They impact him in turn: “Playing characters that are unrelentingly positive can’t help but give you a more positive outlook on life.”

Use your body. If it helps your delivery, don’t be afraid to contort your face, let your arms flail about, rattle your throat with your hand — whatever it takes to nail the emotion.

Spongebob Squarepants official turns 20 years old this month. To mark the anniversary, the cast — which, remarkably, has remained largely unchanged throughout the show’s history — has recorded a special mixed-media episode, “Spongebob’s Big Birthday Blowout,” in which they incarnate their animated characters in the flesh. The hour-long special premieres on Friday at 7pm (ET/PT) on Nickelodeon. The program is dedicated to the show’s creator, Stephen Hillenburg, who died in November from complications from ALS.