Transcript for Papal Appearance: Faithful Flock to Saint Peter's Square
On this sunday, a swelling crowd at the vatican for one of pope benedict's final appearances. There's jackieing tonight among the card nalds and a warning, all cardinals will be told they will not be allowed to tweet when they arrive to choose the new pope. David wright reporting from the vatican. David? Reporter: Good evening, david. It's late, but the lights are on tonight in the pope's apartment. Just look up there. They seem to be the only ones on. Perhaps he's packing up. Earlier today he didn't even acknowledge his imminent departure. But the crowd sure did. At least 50,000 roman catholics came to say goodbye. But pope benedict kept it strictly business as usual. Even though he will appear in that window just one more time, before he makes way for someone else. The crowd was here for benedict today and it matters probably more to them than to him. Reporter: Even before this pope has fully said his goodbyes, behind the scenes the focus has already turned to choosing his successor. A process that has always followed strict rules and is full of intrigue. This weekend the vatican floated a trial balloon, perhaps the cardinals won't wait the usual 15 days to start the election. But from some quarters, strong objections. That only the pope can change church law. And for benedict to do so now might look like he's meddling. His retirement has already shaken the process up. And make sure your retirement years are golden. Reporter: "Saturday night live" parodied that idea. One more change this time around -- twitter. Several cardinals do it. But they won't be allowed to once inside the conclave. Because the vatican doesn't want a tweet to upstage the white smoke.
This transcript has been automatically generated and may not be 100% accurate.