The New York Rangers were cruising along with a two-goal lead midway through the third period and seemed on the way to victory.
Mitchell scored his first NHL goal and set the wheels in motion for a big rally. The Maple Leafs added four more goals against Rangers backup goalie Steve Valiquette in a span of 5:21 to pull out a 5-2 victory over the Rangers on Saturday night.
"It certainly was a burst of energy -- it came all at once," said forward Dominic Moore, one of Toronto's scorers. "It seemed like it must have been pent up. With the fans, as well, they sort of released their [energy] all together."
The game appeared to have slipped away by the time Mitchell was penalized for holding at 10:10 of the third period. The 23-year-old rookie took a penalty but was bailed out in the end.
He skated into the Rangers' zone when the penalty expired and roofed a shot over Valiquette at 12:36.
"I just fist-pumped as many times as I could," Mitchell said. "I was so excited that nothing was really running through my mind, just, 'I scored, I scored, I scored.'
"It was great."
Jason Blake tied it 2-2 at 14:02 before Pavel Kubina ripped a slap shot over Valiquette just 52 seconds later. Mitchell got his second of the night at 16:06 and Moore sealed it with his third of the season at 17:57.
"It's been awhile since I've been in a game that the crowd gets into it that much," Leafs forward Niklas Hagman said. "It was so loud and we were throwing everything to the net.
"I'm pretty sure it put a little doubt in [Valiquette's] mind about what was going to happen."
Valiquette, an Ontario native, has starred against the Leafs in his career. He shut them out through 65 minutes in a 1-0 Rangers victory on Oct. 17 and was just 7:24 from posting another blanking.
"I don't know exactly why that happened," Valiquette said. "It hasn't soaked in yet ... I'm really surprised."
The Rangers are off to the best start in franchise history and entered as the top team in the NHL (10-3-1).
"The trolley came off the tracks with the silly passes and the turnovers in the neutral zone," New York coach Tom Renney said. "We started turning the puck over, and allowed the Leafs to get back in the game."
Vesa Toskala made 18 saves for the Maple Leafs (5-3-3), who have erased two-goal deficits and pulled out wins in three of their past six games.
The Rangers weathered a fairly strong start by the Maple Leafs and managed to kill off three penalties before Callahan got them on the board. The winger scored his fourth goal of the season with 9.3 seconds left in the first period after taking a beautiful cross-ice pass from defenseman Dan Girardi and beating Toskala high with a wrist shot.
Toronto had a couple of good chances to tie it in the second period but Tomas Kaberle's point shot rang off a post, and Valiquette got his glove on a hard attempt from Alex Steen.
Betts matched last season's output with his second goal of this campaign, scored at 15:25 of the second period. Dmitri Kalinin's point shot caromed off the boards behind the goal before Betts tucked the puck in the open side.
"I think we just try and make it hard on ourselves," Mitchell said. "Being down 2-0 is not something that we like but it seems to be working."
When Valiquette started the third period with nice saves on Matt Stajan and Nik Antropov, it didn't look like it would be a recipe for success. But Toronto kept pressing and the flurry of goals soon came.
Mitchell was a plus-4 and had five shots on goal. ... D Anton Stralman was back in the Leafs lineup, but Jonas Frogren, Carlo Colaiacovo and Ian White were scratched. ... Valiquette beat the Leafs 1-0 in a shootout on Oct. 17 ... Toronto forward Jason Blake played his 600th NHL game. ... Maple Leafs rookie D Luke Schenn will turn 19 on Sunday. ... Heading into the night, the Leafs had the fourth-most blocked shots of any NHL team with 162.