Place it immediately after the unknown person's introduction, then follow it with the Vine Boom Sound Effect before cutting to the reaction shot. Keep the sequence short and let the next clip carry the joke forward.
About this sound
This 1.7-second clip captures Conor McGregor asking, “Who the fook is that guy?” in a thick Irish accent, his tone sharp, amused and openly dismissive. It feels like catching someone pretending to matter while everyone else wonders why he is there. McGregor said it at a UFC press conference in 2016, answering Jeremy Stephens, and the line soon became a go-to reaction for unknown or overconfident newcomers.