Katharine McPhee's bachelorette party was so hot that the fire department showed up ... but they forgot to bring clothes.
McPhee's bachelorette party went down over the weekend in London after she finished up a performance of the musical, "Waitress."
The future Mrs. David Foster captioned a photo as, "Not your average backstage meet & greet," and showed a shirtless firefighter dancing over the star whiel she wore a wedding veil.
The Grammy winner and her 69-year-old boo are set to tie the knot soon after getting engaged during a trip to Italy last summer.
McPhee has been married once, while the upcoming nuptials will be Foster's fifth marriage.