April 30 and May 7. Based on reports that continue to come in, these appear to be major episodes in Grey's Anatomy lore.

As we've previously written about, major guest stars and significant wedding developments will take place on these dates. And we can now add a couple of news tidbits to earlier stories:

According to TV Guide, Thatcher Grey invites his daughter and her new boyfriend out to dinner on April 30. Think Mark can play the role of the respectful, well-behaved boyfriend? Or will he end of doing Lexie in the bathroom?

Also: sources say that Derek will deliver a wedding present to Meredith on the May 7 episode. The groom will gift his bride with... her first solo surgery!

AWWWW!

Steve Marsi is the Managing Editor of TV Fanatic. Follow him on Google+ or email him here.