Breaking with tradition, Pope Francis delivered off-the-cuff remarks about God's power to forgive instead of reading from a written speech for the first Sunday window appearance of his papacy.
He also spoke only in Italian - beginning with "buon giorno" (Good day) and ending with "buon pranzo" (Have a good lunch) - instead of greeting the faithful in several languages as his last few predecessors had done.
His comments and humour delighted a crowd of more than 150,000 in St Peter's Square, drawing cheers and laughter.
In just five days, Francis's straightforward, spontaneous style has become an immediate hallmark of his papacy.
Earlier on Sunday, he made an impromptu appearance before the public from a side gate of the Vatican, startling passers-by and prompting cheers, before delivering a six-minute homily - brief by church standards - at the Vatican's tiny parish church.
Before he entered St Anna's Church to celebrate Mass, he heartily shook hands with parishioners and kissed babies.
After Mass, Francis put his security detail to the test as he waded into the street just outside St Anna's Gate.
As the traffic light at the intersection turned green, Francis stepped up to the crowd, grasping outstretched hands. The atmosphere was so casual that several people even gripped Francis on the shoulder. A few minutes later as the traffic light turned red, Francis ducked back inside the Vatican's boundaries to dash upstairs for the window appearance from the papal apartment in the Apostolic Palace.
The studio window was opened for the first time since Francis's predecessor, Benedict XVI, gave his last window blessing on Sunday, February 24. Four days later, Benedict went into retirement, the first pontiff to do so in nearly 600 years.
Francis, the first pope from Latin America, was elected on March 13. He has been staying in a hotel on the Vatican's premises until the papal apartment in the palace is ready.