Erin Moran, who played Joanie Cunningham on Happy Days, has died at 56.

Erin Moran, best known for playing Joanie Cunningham on Happy Days, has died. She was 56.

According to TMZ, Moran’s body was found unresponsive on Saturday. The cause of death is unknown.

The actress, who also starred in the Happy Days spinoff Joanie Loves Chachi, had fallen on hard times in recent years.

She was reportedly kicked out of her trailer park home in the US state of Indiana because of her hard-partying ways.

Many of her co-stars paid tribute to her as the news of her death began to spread.

“Such sad sad news. RIP Erin. I’ll always choose to remember you on our show making scenes better, getting laughs and lighting up tv screens,” tweeted Ron Howard, who played her brother Richie Cunningham on the iconic series.

“OH Erin…now you will finally have the peace you wanted so badly here on earth. Rest In It serenely now…too soon,” tweeted Henry Winkler, who starred as The Fonz.

Don Most, best known as Ralph Malph on the show, said in a statement, “I am so incredibly sad to hear about Erin. She was a wonderful, sweet, caring, talented woman. As I write this I can’t really comprehend this right now. A very painful loss. It gives me some comfort to know that she’s with Tom, Al, Pat and Garry. Rest In Peace, sweet Erin.”

Anson Williams, who played Potsie, said, “Erin was a person who made everyone around her feel better. She truly cared about others first, a true angel. I will miss her so much, but know that she is in God’s hands. RIP sweet angel.”

Moran was just 14 when she signed on to play Ron Howard’s sister in the family comedy, which aired from 1974 to 1983.

“What happened with all of us was like we were this family,” Moran said in a 2009 interview.

“It was so surreal with all the cast members…They were my family, get it?”

The actress, however, apparently wasn’t so positive when it came to Joanie Loves Chachi, which co-starred Scott Baio.

“I liked working with the people. But I didn’t even want to do it. I was talked into it,” she said.

“I wanted to stay on Happy Days. They were running them at the same time.”

The Happy Days spinoff only lasted one season from 1982-83.

Moran’s TV credits also include The Love Boat, Murder, She Wrote and The Bold and the Beautiful.

She most recently appeared on VH1’s reality show Celebrity Fit Club in 2008 and low-budget film Not Another B Movie 2010.

In 2012, Moran and three of her co-stars – Marion Ross, Williams, Most and the widow of Tom Bosley – filed a $US10 million ($A13 million) lawsuit against the CBS network which aired the show, claiming they never received merchandise royalties they were owed.

The case was later settled out of court.