American rapper Jack Harlow is making a star name for himself in American pop and music culture, most recently hosting Saturday Night Live last weekend. The Kentucky native is hugely popular on Instagram with about 6.8 million followers, so it's becoming more common to hear his name mentioned these days.

But even with the newfound star status and large social following, I was still caught off guard to hear Harlow's name mentioned on American Express' (AXP 1.41%) latest earnings call. Earnings calls provide the management of companies with an opportunity to update the public on how the company performed over the prior three months and also update investors on what management thinks might happen going forward.

While they can be incredibly informative meetings, they can also be pretty bland. So when Harlow's name got mentioned, it was certainly an intriguing -- yet also telling -- moment about AmEx's business. Here's why.

Gen Z and Millennials love AmEx

Earlier in October, the 24-year-old Harlow partnered with AmEx to do a concert in Brooklyn exclusively for AmEx card members. The idea is fairly relevant when you think about AmEx's marketing strategy of emphasizing spending on experiences, which seems to be popular among millennials and Gen Z. Millennials represent people born between 1981 and 1996, while Gen Z is anyone born between 1997 and 2012.

On the earnings call, Barclays analyst Mark DeVries asked AmEx executives if there was a jump in new applications because of the Harlow concert. Management seemed to find this amusing, chuckling before answering that they were not aware of how many new card members they acquired from the event.

However, the question is emblematic of how much AmEx leans into a younger audience to drive growth in its business. In the third quarter of the year, AmEx added 3.3 million new card members, making it the company's best quarter for new customer acquisition since the pandemic began. About 60% of these cards were issued to millennials and Gen Z customers.

Millennials and Gen Z also drove AmEx's largest growth in the quarter in its U.S. consumer services billed business, AmEx's largest spending segment. Spending in this category from millennials and Gen Z grew 39% year over year, and AmEx CEO Stephen Squeri is clearly pleased with the company's progress among millennials and Gen Z customers:

I think this whole concept of generational relevance in bringing people into the franchise early and bringing them in on a premium product that they can really embed their lives into has really helped us out tremendously.

The strategy is working

AmEx has leaned into the younger audience, and they are doing it differently than they used to. AmEx's old strategy involved bringing members into the ecosystem with a free credit card and eventually upgrading them along the way.

Now, AmEx tries to get the younger audiences onto premium cards with annual fees right away but does so with a product and brand that identifies more with their exhilarating, experience-laden lifestyles. From there, the company can create more lifetime value. These customers are also apparently very strong from a credit perspective, with AmEx boasting one of the strongest loan books in the industry when it comes to credit quality.

With how focused AmEx is on acquiring younger customers, it's now understandable why DeVries was curious about the Harlow event. And considering the success AmEx had with younger cohorts, it might not be the last time we hear a famous rapper get a shoutout on one of AmEx's earnings calls.