"Jeff Conaway was a wonderful and decent man and we will miss him. My heartfelt thoughts are with his family and loved ones at this very difficult time," Travolta, 57, told PEOPLE.
The actors met on the set of the hit 1978 movie musical Grease. Both actors played members of the T-birds: Travolta was the lead, Danny Zuko, and Conaway played his best friend Kenickie Murdock. The role helped launch Conaway's career, and the movie became one of the screen's biggest-grossing musicals of all time.
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"He was such a sweetheart. I've known him since Nov. 28, 1972!" Henner tells PEOPLE. " We did Grease together before we did Taxi. We traveled in the national company of Grease together, so I was connected to him and worked with him quite a few times. We were like babies together, and then when he got Taxi it was so great. He always reminded me of my brother Tommy, and I always reminded him of his sister Michelle, so we felt a real familial kind of connection."
She called him "the nicest person. He was such a sweetheart. You know, a character – he had this wicked sense of humor but he was so sweet, so sweet, in a way that I think a lot of people don't realize. ... He was just a doll. Oh, we always talked on the holidays and stuff."
And, with that, she broke into tears.
With reporting by MIA McNIECE