other fish to fry
Other things to do; other plans.
They wanted John to be the secretary, but he had other fish to fry.
Mary was invited to the party but she refused because she had other fish to fry.
queer fish
A strange or unusual person who does odd things.
Uncle Algernon dresses in heavy furs in the summer and short-sleeved shirts in the winter. No wonder everyone considers him a queer fish.
standoffish
Stiff; aloof; reserved in manner.
The famous chess player is hard to get to know because he is so standoffish.