db={"people":[{_id:ObjectId("61f9d7dd837c1fb343a21550"),alias:["Lewis","Colt"]}],"report":[{_id:ObjectId("61fc1f59bf1edbf56d24acad"),people:["Lewis","Jake"],Report:"They talked about Python and C."},{_id:ObjectId("61fc29e73cd13b44ffc4074b"),people:["Colt","Justin"],Report:"They tweaked the cogs."}]}

db.people.aggregate([{"$match":{/** put your query here*/alias:"Lewis"}},{"$lookup":{"from":"report","let":{alias:"$alias"},"pipeline":[{$match:{$expr:{$gt:[{$size:{"$setIntersection":["$$alias","$people"]}},0]}}}],"as":"matchedReports"}},{"$unwind":"$matchedReports"},{"$replaceRoot":{"newRoot":"$matchedReports"}}])