Dressed to the nines in formal attire, pop star Perry, 39, had two antennas coming out of her forehead, while actor Bloom, 46, opted for prosthetic ears reminiscent of the ones he wore more than two decades ago in his breakthrough Lord of the Rings role.
The Firework hit-maker tied together her look with a shimmery champagne-toned metallic gown that featured a corset bodice and accordion pleats.
She accessorised with a pair of sparkly, pointed-toe high heels that were the same colour as her dress, and just like her husband-to-be, Perry's ears were costumed in prosthetics that gave them a pointy tip.
Uploading the images to her Instagram account, Perry told her 202 million followers: "Spaced out and starry eyed."
While she offered no explanation as to why they were dressed like that, someone who appeared to know was Kim Kardashian.
Taking to the comments section, the SKIMS mogul wrote: "I was obsessed with this look last night!!!!"
The Kardashians star isn't shy of a selfie or two, so perhaps she will reveal more context soon on her own social media.
Long-time couple Perry and Bloom, who got engaged in 2019 and have yet to wed, first met at the 2016 Golden Globes afterparty and recently celebrated their anniversary.
They share three-year-old daughter Daisy Dove, while Bloom is also dad to son Flynn, 13, from his relationship with Miranda Kerr.