Aargh! This thing annoys the hec out of me with its endless Flash Movies. Additionally...
Kermit and Piggy didn't agree to get married, that was part of the plot ofManhattan Melodies, so it was only part of the onstage performance.
Interestingly, I don't know if this is common knowledge or not, I found the old movie book of Muppets Take Manhattan recently and at the end just after the wedding scene, they show Kermit asking Gonzo why he didn't play the minister. Gonzo admits the man who conducted the ceremony was a real minister and that Kermit and Piggy are now really married! Kermit promptly gulps, shrugs, then goes into "What better way could anything end..."
Plus there's photos of Kermit, Gonzo and Piggy talking, clearly just after the wedding scene. It seems possible that this was the original ending intended, but they backed off of it! This is further strengthened by the fact that we see Statler and Waldorf trying to help Kermit snap out of his amnesia (obviously that wasn't in the final movie either).
Btw, the quiz is great! Not too easy or too difficult. Though they do need to check their answers before posting!