A ‘find someone who' activity is a speaking activity which involves learners trying to find someone in the group who matches a description.

Example
The group are practising using the present perfect for experiences. Amongst the group there are learners who have to:
find someone who has been abroad
find someone who has eaten something really strange
find someone who has done a bungee jump

In the classroom
This is a very versatile activity, which can be adapted to almost any language aim. For example, learners can practise multi-word verbs (‘Find someone who has fallen out with their partner') or character vocabulary (‘Find someone who is a lone wolf').

Further links:

https://www.teachingenglish.org.uk/article/activities-first-lessons-1