Celeb Kendrick Lamar surprised many when he appeared in an online cameo for the ABC sitcom Black-ish. The premise: The TV family creates an online music video they hope will go viral. Lamar helps out by lending the tune of his song “Alright.”

Though the promo’s effect on ratings was negligible, it hints at the interesting possibilities of cross-promotion in the digital and social media age. While cross-promotions like Lamar’s have the potential to broaden viewers’ horizons to artists and properties they might have otherwise been unaware of, navigating a sweet spot between these audiences can be tricky.

Here are three tenets to keep in mind when dealing with digital promos:

1. Promos Are Content, Too

Usually, a celebrity appears in a promo if he or she is planning to actually be on the show they’re promoting. For instance, whoever is guest-hosting Saturday Night Live often shoots about a half-dozen promos.

CBS has had success with promos for The Late Late Show with James Corden. An online teaser of Adele appearing on the show’s “Carpool Karaoke” has garnered over 10 million views, while the full video itself featuring Adele attracted more than 80 views.

The concept of a “promo cameo” is a new approach. Lamar’s predecessor in the promo cameo is, oddly enough, Mitt Romney, the 2012 GOP presidential candidate who last summer promoted the premiere of Late Show with Stephen Colbert.

The lesson learned here is that promos are a form of media in their own right. Promos can go a long way if they are thought of as ads that have the potential to go viral.

2. Promos Can Provide Access to New Online Audiences

As we all know, the internet and social media often have the perverse effect of making us more closed-minded. While we all used to share mass media, these days you can pick and choose the news sources you like and prune your social media feeds accordingly. A 2014 Pew survey, for instance, showed that 66% of politically conservative Facebook users said their friends on the network shared their views. Liberals, meanwhile, were more likely to unfriend someone because of political differences.

The major downside of this is that users’ beliefs are challenged less, and with so many entertainment possibilities, trusted curators are helpful. A friend whose taste you trust can let you know if that new show on Netflix is worth checking out, for example.

The same is true with artists. If you’re a Quentin Tarantino fan and he recommends some obscure Chinese flick, you might just seek it out. If you love Lamar’s To Pimp a Butterfly album and find he thinks Black-ish is cool, you might want to give that show a look. Lamar doesn’t even have to mention his cameo on Twitter. If you’re a fan, the news will surface in your feed.

Cross-promotions these days are a chance to introduce cloistered online audiences to other self-contained communities. The upside for such linkage is huge.

3. Promo Cameos Must Avoid Confusing Audiences

The “promo cameo” also has the potential to confuse fans. Much of the chatter on Twitter about Lamar’s appearance in the Black-ish promo was either wondering if he actually would appear on the show or frustration about the fact that he didn’t.

This is indicative of the delicate needle that must be threaded when planning a digital celebrity cameo. One must determine if they are creating false impressions about the ultimate content that is being promoted. At the same time, shoe-horning a full-on cameo out of obligation can come off as stiff and contrived.

Perhaps one reason why Black-ish’s promo wasn’t quite on point in its execution was that it didn’t fulfill its content’s promise proportionally to the hype it generated. TV executives and digital marketers would be wise to make sure they deliver on the promise made in the promo—while also making sure the ultimate result is organic and in line with the tone of the show itself.

An Interesting and Inspirational Experiment

As it stands now, Lamar’s promo cameo was an interesting experiment that may inspire others. Lessons to be learned include treating promos as distinct sources of viral content, going for crossover appeal, and taking steps to prevent confusion and deliver on promo promises. It would have been fun if Lamar’s promo cameo had gone viral the way the Black-ish TV family hoped their own online music video would but sometimes being first—or near first—is enough.