The egg in Deltarune Chapter 5 appears to be found by repeatedly cutting through the wheat near the cliffs shop until a blue balloon spawns, then following it into a hidden flower puzzle room and continuing left to the Forgotten Man for the egg. The most recent walkthroughs say the key trigger is harvesting the same reappearing patch of wheat several times, then completing the flower sequence the Annoying Dog shows you.

Steps

  1. Go right from the Cliffs shop to the wheat fields.
  1. Run back and forth through the field until one wheat patch keeps reappearing.
  1. Keep hitting that same patch until a blue balloon appears.
  1. Follow the balloon left into the hidden room.
  1. Solve the flower puzzle by matching the Annoying Dog’s order.
  1. Use the watering can to open the path, then go left to the tree and talk to the hidden man for the egg.

Small caveat

A few guides note that the exact flower order can vary, so watch the Dog closely in your own run. One write-up also says the balloon may take several passes to appear, so patience matters more than speed here.

TL;DR

Harvest the same wheat patch repeatedly, follow the blue balloon, copy the flower sequence, then head left to the hidden tree room for the egg.