Pazzini stars in Inter thriller
Second-placed Napoli also put on a show, thrashing Pazzini's now toothless former club Sampdoria 4-0 with rampant Uruguay striker Edinson Cavani netting another hat-trick as they cut the gap with leaders AC Milan back to four points.
Faltering Juventus lost again, 2-1 at home to in-form Udinese, as the gulf in class between the fallen Turin giants and the other top teams continues to be apparent.
In one of the best matches of the season, fourth-placed Inter found themselves trailing to first-half goals from Fabrizio Miccoli and Antonio Nocerino despite dominating.
Pazzini, signed on Friday, was thrown on at the break and soon scored with a superb turn-and-shot before Palermo's Javier Pastore had a penalty saved by fit-again Julio Cesar.
Leaping like a salmon for a trademark goal, Pazzini then planted a bullet header into the bottom corner from Maicon's free-kick and Samuel Eto'o completed the victory from the spot 14 minutes from time after Pazzini was pulled back.
"It was impossible to think it would go like this, it seems like a dream," Italy forward Pazzini told Sky.
"It's been an extraordinary afternoon full of emotion, joy and satisfaction. It's a day that will be difficult to forget."
Inter coach Leonardo, whose side lost their first match under his month-long stewardship last weekend at Udinese, took a big gamble at 2-0 down at half-time by sending on Pazzini and fellow new signing Houssine Kharja.
The European champions were already ravaged by injury and suspension and the substitutions made them even more unbalanced with Pazzini lining up in a front three with Eto'o and Diego Milito which is unlikely to suit his game long-term.
However, in the end, sheer will dragged Inter through and they stay nine behind Milan, 2-0 winners at Catania on Saturday.
AS Roma's game at Bologna was abandoned at 0-0 after 18 minutes because of snow, meaning they slipped to fifth as news of their impending sale seems imminent.
Juventus dropped to seventh as their outside title hopes took another blow after Cristian Zapata and a late goal by Alexis Sanchez gave Udinese a comeback win following Claudio Marchisio's acrobatic opener for the hosts.
Juve's Leonardo Bonucci and Sanchez were sent off late on.
Juve's misfit striker Amauri was omitted amid speculation he could leave on Monday's transfer deadline day with the desperate Turin side keen on Cagliari's Alessandro Matri, who scored twice as the Sardinians beat beleaguered bottom team Bari 2-1.
Brescia coach Mario Beretta was replaced by Beppe Iachini after the second-bottom side lost 3-0 at home to Chievo.
Lecce drew 1-1 with relegation rivals Cesena and mid-table Genoa bucked up having suffered from the sale of their top players with a 3-1 win over Parma.
(Editing by Dave Thompson; To query or comment on this story email firstname.lastname@example.org)