Lateral thinking puzzle asking how one egg remains in the carton after twelve people each take one.

This is a classic lateral thinking puzzle that requires creative and out-of-the-box reasoning. Let's break it down step by step:

Problem Statement:

- There are a dozen eggs in a carton.
- Twelve people each take a single egg.
- After this, there is one egg left in the carton.
- The question is: How?

Key Points to Consider:

1. A dozen eggs: This means there are 12 eggs initially.
2. Twelve people each take one egg: If 12 people each take one egg, you might initially think all 12 eggs would be taken, leaving none in the carton.
3. One egg left in the carton: This suggests that not all 12 eggs were taken out of the carton.

Solution:

The key to solving this puzzle lies in understanding that the wording allows for an unconventional interpretation. Here’s how it works:

- The last person takes the carton with the remaining egg inside: When the twelfth person takes their egg, they do so by taking the entire carton, which still contains one egg. This means the carton itself, along with the last egg, is "taken" by the twelfth person.

Explanation:

- Initially, there are 12 eggs in the carton.
- The first 11 people each take one egg, leaving 1 egg in the carton.
- The twelfth person then takes the carton, which still contains the last egg. Since the carton is now in the possession of the twelfth person, it is no longer considered part of the original setup, but the egg inside it is still technically "left in the carton" (albeit in someone's possession).

Final Answer:

The reason there is one egg left in the carton is because the twelfth person took the carton itself, along with the last egg inside it.

$$
\boxed{\text{The twelfth person took the carton with the last egg inside.}}
$$