It's all fun and games until someone starts a fire.
Then trash cans get tossed, windows get shattered and a city's reputation gets sullied once again.
At least, that's how it played out last October when some fans turned the Broad Street celebration of the Phillies' World Series victory into an ugly, unruly mess.
Philadelphia police officials said they are prepared to keep fans in line tonight if the Phillies clinch the National League Championship Series at home.
"We have our people ready," said police spokesman Lt. Frank Vanore. "We'll be out there."
Last fall, the Phils clinched the NLCS pennant in Los Angeles, and decidedly peaceful celebrations were held on Broad Street in South Philly and at Cottman and Frankford avenues in the Northeast.
Although it seems unlikely that Phillies fans would completely flip their wigs over a win tonight - the ultimate goal, remember, is another World Series title - police plan to err on the side of caution.
Vanore said state troopers will patrol on horseback near Citizens Bank Park, while an untold number of Philly cops will be pedaling around celebration "hot spots" on bikes.
Commanders will keep an eye on any celebrations from Police Headquarters, where they have the benefit of watching footage captured live from the city's 100-plus working surveillance cameras.
Vanore said officials have asked bar owners whose pubs are near outdoor gathering spots to serve their patrons with cups instead of bottles, "so we don't have to worry about projectiles."
He said the Police Department also has asked local universities to warn students about the consequences of behaving badly at any public celebration. (Hint: They will be arrested.)
During the post-World Series euphoria last fall, police encountered trouble as the celebration wore on and genuinely ecstatic fans seemingly were replaced by violent, drunken ones.
One "hot spot" developed on Broad Street near Shunk in South Philly, where fans toppled a traffic pole and set off M-80s, a type of illegal firecracker.
Boorish celebrants also went out of control in Center City, where some looted a luggage store at Broad and Walnut streets, while others damaged planters and taxicabs and started small fires.