Even short frame=by=frame animations require a large number of drawings to create the illusion of motion. So when Jägermeister Spain wanted to create an ad around the idea of an animated tattoo, they also had to commit to finding at least 100 people who would be willing to get a tattoo for the project. This article at Yorokobu (in Spanish) explains how they did it.

An initial call for recruits on social media yielded 1500 volunteers. Producers then selected those who would be most likely to follow through with the commitment to get the tattoo and show up for the shoot after it had healed. Tattoo artists then drew the tattoos to detailed specifications, taking into account how properties of the tattoo's location and skin would affect the look of the final product. For three weeks after the tattoos were applied, the volunteers were called every day to make sure they were following instructions to avoid any distortions to the drawings as they healed. They all gathered in Barcelona to shoot the animation over two days.

You can see photos of some of the people who participated (and their tattoos) at Yorokubu.