Chappell Roan made a surprise appearance at one of Rosalía's Lux Tour shows, joining the Spanish singer for a confessional segment that has become a recurring feature of the concert. Prompted to share something she wanted to get off her chest, Roan revealed the real-life inspiration behind her song 'Casual', recounting a relationship that ended abruptly and left her hurt. The moment drew attention because it offered fans direct insight into the origins of one of her tracks.

Roan appeared at the Oakland Arena on Monday 6 July, describing a pandemic-era flirtation that developed over three months of online contact before an in-person date in Los Angeles. She recalled kissing the person and feeling as though she was "floating", only to be told days later that they had "met someone", and later learning they felt the relationship had been "just casual". Rosalía compared the story to her own song 'La Perla', which follows the confessional part of her set, while other guests including Lola Young, Karol G and Maggie Rogers have taken part in the same segment during the tour.