The excuse was the universe was fairly screwed up at that point so he could get away with things he couldn't otherwise ordinarily do.
But maybe the point was that the Tardis couldn't contain two Amys from two different timestreams (this episode) but it can manage with two Amys from the same timestream (Comic Relief).
Hell, why am I even analysing this, they make it up as they go along.
#7960106, By Dan234 The Official Doctor Who Thread
Dan234 2,245 posts
Seen 39 minutes ago
Registered 9 years ago