An all-purpose phrase
The line is originally quoted from Winnie-the-Pooh from Winnie-the-Pooh, chapter 1. Pooh and Christopher Robin are in the woods and Pooh has a plan to get honey from a bee's nest at the top of the tree. The plan involves Pooh floating up, tied on to a balloon. Christopher Robin asks if they will notice him under the balloon to which Pooh responds:
"They might or they might not," said Winnie-the-Pooh, "You never can tell with bees."