"The Simpsons" creator Matt Groening admitted fans weren't just hearing things if they recognized a familiar voice in a 1991 episode involving a patient at a mental institution.

Many fans thought they heard Michael Jackson's voice in the episode titled, "Stark Raving Dad." In the episode, the psychiatric patient called the Simpson's home and introduced himself as Michael Jackson.

"Hello? Who is this?" the character asks, as Homer Simpson's son, Bart, picks up the phone.

"I'm Bart Simpson, who the hell are you?" Bart replies.

"I'm Michael Jackson," he said.

"Michael Jackson? No way," Bart said.

'THE SIMPSONS' ADDRESSES APU STEREOTYPE CONTROVERSY: 'WHAT CAN YOU DO?'

The patient, a tall, balding man, looked nothing like Jackson — but many said his voice compared to the "King of Pop" was uncanny.

For more than two decades, "Simpsons" fans debated whether that really was the voice of the singer, who died in 2009 at the age of 50. A credit for the character at the end of the episode read "John Jay Smith."

WORLD CUP FANS SPECULATING ABOUT 'SIMPSONS' SOCCER EPISODE

But that didn't prevent producers and staff members from talking about Jackson's guest appearance, though it wasn't officially confirmed by the show's creator until recently.

"We really did have him," Groening confirmed during an interview with Australian TV show "The Weekly" this week.

Groening revealed Jackson himself called him about getting a part on the show, but he initially thought it was a prank call and hung up.

"He has the voice of someone doing a Michael Jackson bit," Groening recalled.

The hit television producer later realized it wasn't a "bit" at all — it was actually him.

"He did the show, he didn't want credit for it — it was some kind of deal with his record company or whatever. So when it came time to sing the songs, he had a soundalike singer. And he stood there and watched the guy who was so nervous, who had to sound like Michael Jackson," Groening said, adding that Jackson giggled in the background.