He's got a knack for saying stupid things, but normally he would have kept as tight a lid on what he let slip to Cory's dad of all people as he did stuff about his mom or half-brothers or anything else he didn't feel ready to show Cory, who'd already witnessed enough idiot stuff that he must be at breaking point.

Or else maybe Cory was getting off on mending trailer trash as a way to avoid thinking about the ever-present Topanga, the only thing capable of screwing him up to a level to match Shawn. Always the over-achiever.

In some sick way, he might be doing Cor a favour, but it sure doesn't feel like it, dealing with Mrs. Matthews' tired disappointment and worse, the painful lack of surprise from Mr. Matthews.

Shawn's dragged Cory down to his level again, and the confirmation of what he already knew, that Mr. Matthews has never, will never think Shawn good enough for his perfect son; is as sick as Shawn of seeing Cory's loyalty paid back with yet another failure to live up to it, makes his guts twist as much as the queasy, sour booze aftertaste.

Sure, this time, and breaking the habit of a lifetime, it was Cory who was the screw up, but he hardly had to twist Shawn's arm to go along, to blow off the party of the year and even Angela without a second thought; especially when it was Shawn who'd made Cor feel like shit in the first place, ragging on him about Topanga.
Cor never gets impatient when Shawn has one of his semi-regular dramas, and if Shawn had been responsible, like usual, Cor would have staunchly defended his honour in the face of obvious and overwhelming guilt.

Shawn instead, still buzzed, and pissed at Mr. Matthews, makes a cheap shot; and gazes insolently and unbreakingly, raises his eyebrows and with a leer, drawls 'He wanted to feel good, and I showed him how.'

Mr. M's always been a little more on the ball than the rest of the family about Shawn, Cor included – no, especially; because the allusion doesn't fly over his head like oblivious Cory and his mom; and he looks like he wants to hit Shawn.

This at least is something Mrs. M doesn't miss, she drags him away, and Shawn tries to enjoy the small, petty kick he got from needling Cory's dad (and maybe a little from the reference), because he already knows what their earnest parental ruling that Cory will of course, as the dutiful son comply with.

The obligatory grounding will go without saying, so keen will Cory's parents be to inflict the true punishment, get to the real issue.

Shawn only wishes he had half the influence over Cor that his parents believe he possesses. Cory would have listened to him about Topanga, would be alert to the hints he's dropped, over and over. And they say Shawn's the dumb one.

He knows at least that Cory will fight to keep him around, but against his own parents rather than one of Shawn's anonymous, interchangeable girlfriends?
Cory will go to long lengths for Shawn, beyond what he deserves, and he will forgo his usual honesty and lie to his family and Topanga to protect him, but the only thing he's never asked of Cory – and he has no pride when it comes to asking Cory for things – is to make a choice he knows he'd lose.

Instead Shawn makes a last ditch feeble attempt at pacifying Mr M, going along with it all, knowing, or maybe just hoping meek acquiescence will spur on Cory's defiant streak, relying like he has before that if he shows Cor enough times that he won't ask him to choose between him and Topanga, him and his brother, him and anyone and anything else in his life who means more to him than Shawn (and the fact that this list is short does little to comfort Shawn, who's always been greedy, and who's certainty, that Cor was the most important person in the world to him, he lacks about everything else in life - school, family, even girls.)

Relying on playing the good guy, knowing a real good guy wouldn't feel this way about his best friend, wouldn't resent the other people in the first place.

It works, to a point, although Cory's melodrama about Topanga, whiskey-influenced though it may be, doesn't help the encroaching nausea, but Cory's dad relents a little, patting Shawn's shoulder, although his eyes still scan Shawn's face shrewdly as Shawn hangs his head, his hand warm and heavy on Cory's arm.