I ordered a chicken and an egg from Amazon. I'll let you know.
Why this joke works
A Delivery Test for an Old Question
The line borrows the familiar question of which came first, the chicken or the egg, then treats it like a delivery-order problem. “I'll let you know” quietly promises an answer when the packages arrive, without explaining the old debate. Deliver the first sentence as ordinary shopping news and pause before the second. That small delay gives listeners time to recognize both items before the hidden question clicks. No extra explanation is needed once the order is placed.
A closer look
The Experiment Ends Before the Packages Arrive
The first sentence treats two living-system mysteries as ordinary online purchases. Naming a familiar retailer makes the delivery race feel measurable and current, while the second sentence withholds any result. “I’ll let you know” invites the audience to supply the ancient question for themselves. That unfinished promise is the punchline: shipping order is offered as evidence for biological origins.
Fact behind the joke
A Hen Takes About 25 Hours to Form and Lay an Egg
USDA says the interval from ovulation to laying is about 25 hours, followed roughly 30 minutes later by the start of another egg-making cycle. A hen therefore cannot produce a new egg exactly every 24 hours indefinitely. The delivery joke asks which package arrives first, while real egg production follows a repeating biological sequence inside the bird.