Character Analysis
The traditional Greek chorus is present in the form of the titular clouds (Strepsiades, who thinks anatomy is hi-larious, would giggle at "titular." And, um, we're actually giggling right now). The Clouds serve the chorus's usual function of commenting on the action from a kind of removed position.
In addition to weighing in on the wisdom/morality of the characters' actions, the Clouds actually get involved in what's happening and guide the characters, sometimes using more than a little trickery to achieve their ends.
They are (Kind of) Gods
Introducing Strepsiades to the Clouds, Socrates says, "These are the only gods, my man; and all the rest are fantasies" (365). And hey, they talk and live in the sky, so we can imagine drawing that conclusion.
Like gods, the Clouds definitely feel like they have the right to pass judgment over what happens on earth. They make little comments throughout the play about whether something the characters are doing is a good or bad idea. Sometimes they even demand that the characters justify their behavior to them, as when Pheidippides beats Strepsiades:
"Now's your chance, you word-mechanic, shooter of the latest rap: / find a way to talk us into thinking what you did was right." (1396-1397)
Pheidippides uses his newfound Thinkery logic to argue his way out of getting blamed, but the Clouds don't seem convinced.
Tricks are for Clouds?
Of course, you might be asking (as Strepsiades does toward the end) just why the Clouds didn't warn Strepsiades and Pheidippides away from the Thinkery in the first place, if they were so into commenting and had a strong opinion. The Clouds respond that that's just not the way things work around there:
"We do the same thing every time we see / a man who's fallen in love with what is wrong; / we cast him down in sheer calamity until he learns devotion to the gods." (1458-1461)
So, yeah, it's a little tricky, but gods of all stripes have a long and storied history of playing with mankind, especially in Greece.
They're a Fluffy Mouthpiece
One more important thing to know about the Clouds: they speak for the author here and there. There's a part of the play called the parabasis in which the chorus speaks to the audience and talks about larger issues and whatever the playwright wants to get out there among the masses. Since the Clouds are the chorus here, they get to serve in that capacity for this play.