在家里組織朋友聚會的時候，我們一般都會讓關系好的朋友早點兒來，一來他們可以幫忙干點活兒，二來，也能幫主人招呼客人。這樣的聚會賓客在英語中叫buffer guest。

A buffer guest is a close friend that you invite to a party ten or 15 minutes before the rest of the guests are scheduled to arrive.
Buffer guest指關系較近、聚會時要求比其他賓客提前10到15分鐘到場的朋友。我們可稱之為“暖場賓客”。

This guest or group of guests is meant to 1) make it seem like the party has already begun and good times are to be had, and 2) make it less awkward in case someone you don't know particularly well arrives before everyone else.
安排這一類暖場賓客主要是為了：讓后來的賓客感覺聚會已經開始，歡樂時光正在繼續；如果有主人不太熟悉的賓客提前到了，也能幫著調節氣氛。

For example:

I invited Jona over as a buffer guest in case Tim or Josh came over early, because I don't really have a lot in common with them.
我請了Jona過來做暖場賓客，以防萬一Tim或Josh早到，他們跟他們又沒什么共同話題。

（中國日報網英語點津 Helen）