He did make mention of him being Father Christmas when he was with Rose. So it could be the list of the kids gifts. Also I made my mom and Dad write christmas lists so my brother and I can "help santa" this year.
David Tennant tells a Knock Knock joke. David Tennant tells a Knock Knock joke when hosting a Dr. Who themed "Never Mind the Buzzcocks" episode. Cathe dr who David Tennant buzzcocks knock knock Never Mind the B Wilfred Mott
So, I just realized that this is the only time Rory (or the Doctor) got to see his wife pregnant. She was kidnapped by the Silence soon after she found out she was pregnant with River, and was never able to have children again.