Starscream's and Octane's voices are switched in the scene immediately following Galvatron's duel with Rodimus Prime, when Octane is talking to Starscream (in Cyclonus' body) in Galvatron's throne room. We hear Starscream's voice when Octane speaks and Octane's voice when Starscream/Cyclonus speaks. They go back to normal when Galvatron enters to yell at them.