Place it at the exact moment a familiar character returns, then follow it with the Dun Dun Dun sting to underline the reunion before the scene moves on, and save a Vine Boom for the reveal that follows.
關於此聲音
This short two-second clip is GLaDOS speaking the line 'Oh, it's you' in her calm, flat robotic voice, with a slow, unimpressed delivery that makes the greeting feel like a cold welcome back. It is dryly funny and a little unsettling, perfect for a sarcastic hello. The line comes from the artificial intelligence in Portal.