In Peter Pan, a pirate says, "Here we are collecting barnacles on this miserable island!", the joke being that they were so inactive that barnacles were growing on them.
Well, when I first saw the movie, I didn't get the joke and I thought he meant collecting like you collect stamps or whatever. I thought he was implying that they were so bored that they could only do silly things like start a barnacle collection.
A childhood belief about films

others believed things like this
- When I first started learning to read I was convinced that vowels were called barnacles.— Andy Howell
- That the tooth fairy drove around in her green Volks Wagon Collecting teeth from all the children.— Wanda Trytten
- I thought when Grandma's hens were cackling, they were giggling about some private joke in the henhouse. — Not a farm kid
- i used to spell eight "ate" cuz of the stuped: why was six afraid of seven, cuz seven ate(8) ten joke...— 8
- I used to think that growing pains meant that a tomato plant was growing in your stomach.— Annette
- I thought you were supposed to take money out of the collection at church.— Wangchuk