Place it at the turn of a skit, right after the goofing-off montage and just before the serious part begins. Follow it with the Law and Order Dun Dun sting to underline the shift, and keep a second reaction clip ready for the next beat.
About this sound
This 1.7-second clip is one spoken sentence, the words 'We're not really here to have fun, you know' said as a plain statement. It feels dry and faintly awkward, the kind of line that makes a lighthearted room pause for a beat. Its bluntness gives it a scolding edge, turning a casual moment into a reminder that the mood is supposed to be serious.