How far do slaves contribute to the success of Greek and Roman comedy?

In my opinion I think that slaves contribute to the success of Greek and Roman comedy, seen through the importance of the roles that the slaves play in both; The Old Cantankerous and The Rope.In the Old Cantankerous the slaves are a major part of the play, clearly displayed as they make up half of the cast, and collectively have the most monologues. The stock slave will generally be very clever and talkative. He usually is very cheeky which adds humour to the play as it engages the audience. The slaves are very useful as they usually drive the plot forward; this is displayed in The Rope through Sceparnio who tells Labrax and Charmides about the two shipwrecked women in the temples. and in the Old Cantankerous where the slaves are who discover the truth at the end of the play.