Bandmembers Dean and Rob DeLeo axed the Pilots' original lead singer Scott Weiland back in February (13) and have yet to find a permanent replacement - so they opted for Bennington for the night after recently working with him on a new track, Out of Time.
The rocker performed a series of the band's classics, including Vasoline, Sex Type Thang and Wicked Garden during the unannounced set, which came between Vampire Weekend and Thirty Seconds to Mars' sets.
Bennington recently revealed he reached out to work with the Pilots after growing up a fan of their music, saying, "I've loved Stp since I was 13 years old and they've had a huge influence on me. When the opportunity came up to do something creative with them, I jumped at the chance. The guys in Linkin Park have been incredibly supportive of me undertaking this project."
The Weenie Roast festival regularly features surprise sets - Soundgarden appeared unannounced last year (12), while the Foo Fighters secretly hit the stage in 2011.