wear thin

does the Pope wear a funny hat

Obviously! Rhetorical question in response to a question where the answer is an emphatic yes.

have a thin time of it

To be in a difficult or precarious situation due to one not having enough money.

if the shoe fits, wear it

If a description fits, it is probably the case; if an insult accurately describes you, you must bear it; if you take offence at an insult that was only implicitly directed at you, you admit the insult is true enough to be recognizable.

on thin ice

Dangerously, hazardously, delicately.

out of thin air

From nowhere or nothing; from a non-existent or unknown source.

skate on thin ice

To be (or to place oneself) in a risky, potentially dangerous or delicate situation.

spread oneself thin

To commit oneself to too many projects, so that there is little chance of completing them all satisfactorily.

thick and thin

Both good and bad times.