For the game's fictional hard rock band Star-Lord, Eidos Montreal's Senior Audio Director Steve Szczepkowski ended up singing the band's songs himself until a proper singer could be found. However, the game's creative director, after hearing the temp tracks and asking who sang them, was shocked and pleasantly surprised to learn it was Szczepkowski himself and the dev team ended up using the Szczepkowski vocals in the final release, much to his delight.
Contributed by PirateGoofy