The Tampa Bay Rays first baseman's base hit up the middle with two outs in the top of the sixth scored B.J. Upton and tied Game 5 at 2.
More importantly, it bailed out Major League Baseball on a night that will be remembered more for its disastrous field conditions than any single play.
In an unrelenting downpour that was accompanied by swirling 16 mph winds, the Rays and the Philadelphia Phillies attempted to survive and complete Game 5, but it was suspended after the top of the sixth with the score tied at 2.
It will be resumed in Philadelphia with the Phillies batting in the bottom of the sixth, perhaps tonight. But that depends on the weather. The local forecast is for a 90 percent chance of rain most of today and a 30 percent chance of rain tomorrow.
Game 6, if necessary, is scheduled for tomorrow in St. Petersburg, Fla., but might have to be pushed back.
"We'll stay here if we have to celebrate Thanksgiving here," said commissioner Bud Selig, who said pre-game weather reports indicated the game could be completed.
According to baseball rules, if the Rays had not scored in the sixth and the game were called, it would have been considered a complete game - and a Phillies World Series-clinching victory.
For that reason, Selig said there were no plans to end the game. Instead, it would have remained in a delay - for as long as needed - until it could be resumed.
"The game would have been in a rain delay until weather conditions allowed us to continue," he said. "And that might have been 24 hours or 48 hours or who knows," Selig said.
He later added: "I would not have allowed the World Series to end this way [without completing nine innings]."
The rain was steady even before the first pitch but intensified as the game continued, creating puddles throughout the infield. In the fifth, Phillies Gold Glove shortstop Jimmy Rollins was charged with an error when a routine pop-up darted and swirled and eventually hit the heel of his glove and bounced away. The mound and batter's box, however, were in playable shape, according to umpire crew chief Tim Welke.
"That was never compromised," Welke said. "Guys weren't falling off the mound pitching, delivering, and the hitters weren't slipping out of the box, and that was never compromised. ... But due to just the velocity of the rain [the grounds crew] couldn't keep up with keeping the field."
After Pena's game-tying single - and a subsequent out by Evan Longoria - umpires suspended play.
Fifteen years and four days after the Toronto Blue Jays' Joe Carter hit a Series-clinching homer to beat the Phillies in Game 6, Philadelphia was half a game away from celebrating a World Series championship.
The city, and the drenched announced crowd of 45,940 raucous fans, will have to wait.
Selig confirmed that the game would be picked up again at night - about the normal 8:30 start time. Exactly when will be announced as soon as possible to give fans a chance to attend.
Rays left-hander Scott Kazmir, who allowed a two-run single to Shane Victorino in the first inning and then escaped jams until he was removed in the fifth, is the only player on the two rosters who is not eligible to play when the game resumes.
Technically, Phillies ace Cole Hamels, who allowed five hits and two runs through six innings, is eligible. But he threw 75 pitches and will not be used.
"Naturally, we're not happy that Hamels is out of the game," Phillies general manager Pat Gillick said. "But one of the strengths of our ballclub is the bullpen."
Gillick added: "There was a change in the weather, and unfortunately those things happen. So we'll just have to go on from here and go get them whenever we can play."