I was late to class, because I was abducted by aliens
I was abducted by aliens, because they were looking for intelligent life on earth
They were looking for intelligent life on earth, because they hadn't found any yet
They hadn't found any yet, because they were looking in a rural area without many people
They were looking in a rural area without many people, because they were afraid of tall buildings
They were afraid of tall buildings, because their saucers couldn't fly very high
Their saucers couldn't fly very high, because they were full of chocolate bars
They were full of chocolate bars, because even aliens can't resist chocolate
So the reason I was late to class was because aliens can't resist chocolate.
These silly poems trace back reasons (or excuses) for something that happened, by repeating the last event that was explained and then giving a reason (or excuse) for that explanation. This is repeated until you finish with a ridiculous reason for the original event that happened.