In Titus 1:12, Paul cites a Cretan prophet who said "Cretans are always liars, vicious brutes, lazy gluttons."
His name is Epimenides.
The bad reputation of the Cretans come from their claim that they have the tome of Zeus (thus saying that he is mortal). Most people then think they are liars because they think of Zeus as immortal.
The same quote is also found in Acts 17:28.
This verse is also famous for the Epimenides paradox. There is an inherent logical inconsistency because Epimenides is a Cretan. To make a statement that Cretans always lie will make a paradoxical statement because here is no way to assign a consistent truth value to it. It is neither true nor false. Hence some mock at Paul for saying that Epimenides' statement is true (Titus 1:13).