Matt Dillon's 'Modern Family' Guest Spot: There's Something About .....Dede?

Leave it to ABC's "Modern Family." Just when we thought we've seen it all (and we have, haven't we?) they go and give us a storyline that addresses one of the biggest taboos ever: Mom hooking up with her daughter's former boyfriend.

It's baby Lilly's birthday and that means a princess birthday party with all the trimmings. It also means a visit from Grandma Dede ( Shelley Long ), who just happened to run into Claire's high school boyfriend, the smarmy Robbie Sullivan (played by guest star, Matt Dillon ) on her way into town.

As usual, Dede is just full of surprises. Once she gets to Phil and Claire's house, the doorbell rings and there's the ex-beau, all decked out in his limo driver gear.

Matt Dillon's Robbie is about as sleazy as they come. He's sure that Claire ( Julie Bowen ) still "wants" him. He talks about old times- and Claire's high school fast times- as he sits with her kids at the dinner table. Claire can't get the wine down her throat fast enough.

But here's the kicker. Now that he finds out that Claire is married, Robbie is over her. Big time. Claire catches him making out with her mom and we find out later that they had breakfast together. Yuck.

Fast forward to baby birthday party day. Things are going swimmingly, but nervous dad Cameron ( Eric Stonestreet ) wants to breathe new life into the party by dressing up as his alter ego, Fizbo the Clown. Mitchell ( Jesse Tyler Ferguson ) won't have it. The perky Cinderella he hired is the entertainment. Cam disses Cinderella and her fairy dust, telling her to "Never go out of character" when she tells him he can pay her by check.

Meanwhile, Jay (Ed'Neill) has had about enough of this Robbie Sullivan joker. When he shows up with Dede at the birthday party, Jay tells him it's time for him to go. Sullivan puts up a half a fight- apparently he's getting some strong vibes from Cinderella- but finally he slithers on out of there.

Jay's wife, Gloria ( Sofia Vergara ) has her own problems. In order to cope with Jay's ex-wife Dede's presence, she's taken her very first Xanax. With a shot of tequila.

And later Dede lets loose on what's still bothering her all along. In a repeat performance of her first visit to the Pritchett house after Jay married Gloria, Dede lunges at a practically incoherent Gloria for a girl fight. Rarrr.

"Modern Family" airs on Wednesday nights at 9:00 pm ET on ABC.