What does this joke mean?

When grinding a kitchen knife on the fourth floor, I accidentally dropped it and cut it to the third floor. At this time, JJ fell on the green paint brush on the second floor, and the rolled and dyed JJ was blown by the wind and rolled into the cucumber pot on the first floor. The landlord on the first floor got up for a long time and was about to pick fresh cucumbers to eat. He vaguely saw a yellow ripe one fall into the pot and picked it up and ate it.