The Gemoro Brachos 55b says:
"No one has ever had a dream of an elephant passing through an eye of a pin."
How did Pharaoh dream the thin cows swallowing up the fat cows?
Upharoh Cholem and not Cholam. Cholem is present Cholam is past tense.
The Chasam Sofer writes the reason it says Cholem (present) to tell us that Pharohwas a dreamer, he always used to dream . He would not get excited with normal dreams.
The reason these dreams did worry him,was because it was unusual and abnormal .
It was like a dream of an elephant walking through a pinhole. He realized this can't be a dream. It must be message coming from a higher up.