The meaning is not a known or standard English idiom, but rather a reference to the character's preparedness and simple wisdom.

The origin in Paddington Bear

In the beloved stories by Michael Bond, the bear from darkest Peru is always prepared. He stores a marmalade sandwich under his hat, saving it for a moment of need. This detail illustrates Paddington's kindness, resourcefulness, and readiness for a mishap.

Meaning in context

If you hear someone say "all you need is a sandwich and a hat," they are most likely referencing the Paddington quote to suggest:

• Being prepared for any situation.
• Having a simple plan to fix a problem.
• The importance of small comforts during a tough time.

Misinterpretation of other phrases

The phrase may also be mistakenly associated with other idioms:

• "All that and a bag of chips": This idiom, which describes someone or something as "complete" or "deluxe," has an American origin and is unrelated to hats or sandwiches.
• Idioms about being confused: The phrase is not related to idioms that use hats to mean "confused," such as "put on your thinking cap".