Zac Efron thought he was suffering from gas when he had appendicitis.
The 21-year-old star, who was filming new movie '17 Again' when he was taken ill last year, claims his co-star Thomas Lennon didn't take his ailment seriously and urged him to take digestive supplements for trapped wind.
He said: "I didn't know what it was at the time and I was just trying to get through a day's work. Thomas kept telling me, 'Dude, just eat some Beano - it's gas, eat Beano.' And I'm like, 'I don't think so, it doesn't hurt like that.' And he's like, 'No, I swear, if the worst comes to the worst, hang upside down.' "That was Tom's advice. He's like, 'Go hang upside down in your trailer,' and I'm like, 'What?' "
Zac eventually decided to get some rest to try and shake off the problem, but it wasn't until he spoke to his father he realised how seriously ill he was.
He told the Los Angeles Times newspaper: "I fell asleep and, when I woke up, I was completely soaked from head to toe because I was sweating. I was like, 'Something's definitely wrong', and I looked in the mirror and my eyes were like bloodshot and I was very pale and I was like, 'Hmm, something might be off here.'
"So that's when I called my dad and I was like, 'Hey, Dad, what do I do for extreme stomach pain?' And he said, 'You go to the hospital.' "
Zac was eventually taken to Los Angeles' Cedars-Sinai Medical Center where he had his appendix removed.