if pigs had wings

clip someone's wings

To restrict someone's freedom.

make pigs and whistles of

To ruin (something); to make a severe mess of (something).

pigs can fly

Alternative form of pigs might fly.

pigs might fly

A response (often with a hint of sarcasm) to a situation which one thinks that there is no chance of ever occurring.

singe one's wings

To sustain harm, loss or ruin by doing some risky or perilous deed.

spread one's wings

To experiment in life; to find out what one is capable of; to try new things or activities.

wait in the wings

To be about to become important or central.

when pigs fly

Never.