"It's Always Sunny in Philadelphia" fans flocked last night to catch a glimpse of stars Rob McElhenney, Kaitlin Olson and Glenn Howerton outside Mac's Tavern (226 Market), where they attended a grand-opening party.

South Philly-raised McElhenney and Olson, his wife and co-star, are expecting a baby boy in August.

The couple had a great time shooting in town this week, although McElhenney says he wishes they hadn't picked the hottest week of the year to shoot. Olson said she's become insufferable while pregnant, but she seemed sweet to us.

They said the bar won't be too gimmicky, though there are "Sunny" references throughout the place and on the menu.

On the FX series the gang runs a bar called Paddy's, and McElhenney's character is named Mac. Howerton says he's been accepted as a Philadelphian from the show's several trips here to shoot. He worked in a play at the Walnut Street Theatre nine years ago. Castmate Danny DeVito arrived later carrying takeout bags from Butcher & Sunger (15th and Walnut). Guests at the invite-only party included Ryan Howard and Chase Utley, who shot for the show Monday at Harrah's in Chester,  former Phils catcher Sal Fasano and 93.3 WMMR's Preston Elliott and Marisa Magnatta.

At one point Utley's wife Jennifer asked a bar employee "Where's Ryan?" and was told he was "In the back with all the girls." She turned to her husband and said "I told you!"