Back in the day, waitress Cassie Gaffney had an eye-popping bar trick that she once performed for her boss’ grandson Chris Mullins Jr. at McGillin’s Olde Ale House in Center City.

“I distinctly remember being a kid and her taking her glass eye out and putting it her mouth. It was like, ‘Whoa!’” Mullins said. “We still laugh about it to this day.”

But these days, Mullins is Gaffney’s boss.

For 43 years and three generations of owners, Gaffney, 71, has worked at McGillin’s, making her the longest-serving waitress at Philly’s oldest-running bar. The lifelong South Philly resident who lives just off Two Street is so beloved she gets all the important South Philly holidays off.

“Not only does she take off on New Year’s Day but also the day after New Year’s Day because it’s her recovery day,” Mullins said.

Nodding in agreement, Gaffney launched into her best Mummers strut.

In 2017, Gaffney’s granddaughter Shana Barrett, 19, also joined the staff of McGillin’s. On Fridays, the duo work the lunch shift together, the only time their schedules overlap, doling out shepherd’s pies, beer, and cheesesteaks.

“If [customers] don’t know she’s my grandmother, she’ll tell them,” Barrett said.

On Sunday — Mother’s Day — Gaffney will celebrate her 72nd birthday, but she has no plans to cut back on her three lunch shifts per week and bartending duties at private events.

“People ask me, ‘When do you want to retire?’ I can’t answer that because I enjoy coming to work, I enjoy people,” she said. “I think I’ll retire when my body tells me to retire.”

Gaffney, whose birth name is Catherine, grew up in South Philly with 10 brothers and sisters. In 1959, when she was 11, she lost an eye when a group of kids hit her with a stone while she was taking out the trash.

Back then, it was the kind of tragedy that made the news. When a story about “Little Cathy Albert” (she hated that name) ran in the Philadelphia Daily News, hundreds reached out to offer assistance.

“One woman offered Cathy four artificial eyes that her grandson had outgrown,” the newspaper reported.

Mummers even came out to serenade the girl and raise money for her family.

But Gaffney never felt special. She still doesn’t.

So we’ll let her boss explain:

“She worked for my grandfather!” said Mullins, who now runs McGillin’s with his parents, Mary Ellen and Chris. “It’s hard to maintain any employees for a long period of time but for three generations is incredible. You get people who come in year after year or every five years and ask if Cassie is still here.”

Gaffney started at McGillin’s in 1975, after her two kids began grade school. A friend working at the bar helped her snag the job.

“The application was 'Start peeling eggs. Make egg salad,” she said.

Back then, McGillin’s had a sandwich board at the bar where four women, including Gaffney, made sandwiches during lunch. She worked that for 10 years and when her kids started high school, Gaffney put on an apron and began waiting tables. She’s sweet and tender with her customers but is also quick to joke if they pave the way.

Gaffney’s husband, John, who died in 2004, was always supportive of her job. She still misses him like crazy.

During the years Gaffney has worked at McGillin’s, three of her friends met their future husbands at the establishment and one — a coworker — even got married at the bar. Instead of serving tables that day, Gaffney served as the maid of honor at the wedding.

When it comes to theories about why McGillin’s seems like a hotbed for romance, Gaffney has one.

“You get alcohol and male and female and there’s always going to be a connection,” she said.

Gaffney will never forget the engagements she’s witnessed at the bar, the times she’s had to stop people dancing on chairs, or the week when MSNBC’s Morning Joe aired live from McGillin’s during the 2016 Democratic National Convention.

And though she tried to be on her best behavior for this interview, glints of her beautifully bawdy South Philly personality did shine through. There’s the crass but endearing nicknames she and the bartender have for each another, which are not suitable for print; her love of cosmopolitans and Michelob Ultras; and her annual trip to Keenan’s Irish Pub in North Wildwood for an all-class grade school reunion.

“I like to party,” she said.

Gaffney is also no stranger to a Kenny Chesney concert — and the accompanying epic tailgate parties.

“She really is a wild woman. She’s probably one of the funniest, craziest people, in a good way,” Mullins said. “If you ever wanted to sit and have a cocktail with anybody, it’s her because she’s real and she’s hilarious.”

Her granddaughter agreed.

“She’s a cool grandma,” Barrett said. “You can easily talk to her, you can easily hang out with her. It’s just always fun.”

Mullins and Barrett both hope they’ll be working alongside Gaffney for many years to come.

“I told her if she ever becomes infirm and she can’t walk, we’ll wheel her in,” Mullins said. “If we are the reason you can live a happy, long life and it gets you up in the morning and it’s fun, then I’m so thankful that you’re here every day.”