Danny DeVito used to smoke marijuana with Michael Douglas.
The 67-year-old actor became great friends with the 'Wall Street' star in 1966 after bonding over their mutual love of the drug while they were both trying to make it big in Hollywood.
He said: ''We met at a playwrights' conference in Connecticut in 1966. Michael was out there for the summer and was had a really big connection.
''(We bonded over) pot! I was a hippy and so was he, and we were the only ones. So we'd just hang out together and get ripped.''
Danny - who voices Dr Seuss' loveable furry title character in animated adaptation 'The Lorax' - has come a long way since his hippy days and is now an active environmentalist, which he states as a major reason for accepting the title role.
He explained to The Times newspaper: ''It's a message of sustainability that's very strong. And while the rainforests are still being decimated, it's a good dialogue to open up with your kids.
''It's like the Lorax says, put something back into the Earth. And make somebody smile!''
'The Lorax' also features Zac Efron and Taylor Swift and is released at the end of July.