“Challengers” has been one of the most well-received movies of the year so far. It currently has an 89% rating on Rotten Tomatoes and, anecdotally, it’s a frequent conversation topic on social media.

Whenever anything gets big enough in the pop culture zeitgeist, there are people looking to capitalize on it, often through physical media and promotional products. Think about the rise of print-on-demand in promo, which allows entrepreneurs to pounce on sports moments or meme-worthy one-offs in a hyper-connected world, where the only real monoculture is the discussion of culture itself.

With “Challengers,” the materialization of products has come in the form of T-shirts. One is a recreation of a tee that actress Zendaya’s character wears throughout the movie (which seemed to have gained steam from the trailer alone), and the other is a clever faux souvenir from the fictional tournament in the movie.

The “I TOLD YA” T-shirt, in black block lettering, has been a standout. It seems basic enough, but it’s from designer brand Loewe, and costs $330. Even with the high price for a tee, it’s currently sold out in all sizes. But, not to be deterred, online sellers created pretty much identical versions on sites like Etsy for as low as $7. (Or, as Loewe as $7, one might say).

Also on Etsy, shoppers can find a T-shirt commemorating the fictional New Rochelle, NY, Challenger tennis tournament, where the main characters in the movie face off. The shirt is especially notable, perhaps, as it represents the expansion of a movie’s universe into the real world, turning fiction into a tangible product reality. There are examples of this with other intellectual property (IP) items, like “Stranger Things” bringing T-shirts the characters wore into the marketplace.

The tournament tee is smart marketing for “Challengers” too, even if it’s a knockoff. It’s a conversation starter, where someone might ask about the tournament and find out it’s a reference to the movie. Then they watch it. And it’s more subtle, and perhaps therefore cooler, than having a T-shirt with just the movie poster or a photo of the main characters. It has that “if you know, you know” exclusivity, but with the end-result of everyone knowing.

For promo distributors working on campaigns for movies, TV shows or other creative IP, a key takeaway is perhaps this: Take the time to learn about that IP. At the very minimum, watch the show or movie, or play the game. Pay attention to small details that people pick up on, and expand on them. It could just become a must-have product.