'Desperate Housewives': Which Wisteria Lane kid was switched at birth?

james-denton-desperate-housewives-320.jpgSeason 6 of "Desperate Housewives" has come and gone, leaving us with a whole summer to wonder which Wisteria Lane kid was switched at birth. 

Our first thought?

It must be M.J. Delfino. 

With the return of Paul Young (Mark Moses) at the end of Sunday's (May 16) finale, M.J. seems like the obvious choice.

Paul has a motive. He probably blames Mike Delfino (James Denton) for the loss of his son Zach, who disappeared with his dead grandfather's money not long after he found out that Mike was his biological dad and that Paul had stolen him when he was a baby.

Switching Mike's brand new infant boy at birth seems like a pretty good way to get back at him, no?

Of course, if that's true, Paul has technically robbed Mike of two sons and we're not exactly sure how that's fair, but things in Fairview often aren't.  

So, what do you think? 

Is M.J. the kid who was swapped at the hospital? Or is that too obvious? Could it be one of Gaby's little munchkins? Lynette's? Danielle's little Ben whom Bree pretended to carry? 

Weigh in with your theories in the comment section...