I imagine English learners come across phrases like “You’re pulling my leg, right?” or “Don’t let the cat out of the bag,” that might not make sense unless explained first. Japanese (as I assume every language) has many expressions/idioms that need explaining what they mean as well.
To want something very badly. Long ago it was a saying implying to want food so badly it’s as if hand could come out of the throat and grab it (or more like thrust your face in the food and eat without your hands), but now can imply wanting anything besides just food.
Destined to be together. There’s a legend that people who are meant to be together are attached pinky to pinky by a red string (that can’t be seen).
Much like the English expression “piece of cake”, implying something is so easy it could be done before breakfast.
To overhear something. The 小 used here is an old prefix roughly equivalent to “ちょっと”, so it doesn’t mean “little ear” like it may seem.