We have a saying "Abdullah gets all super pepped up in a stranger's Wedding" which means a person gets absolutely excited about some one else's cause which he logically isn't concerned with. Do we have any equivalent in English.
Normally any person wouldn't get as excited as much as the groom & bride, the parents and all those involved in the wedding. But this unrelated person/stranger gate crashes the wedding and gets too much involve and too excited about everything thats happening as those it is his wedding. It is as though you shouldn't get involved (physically or emotionally) and help others where it is not warranted or where you are not invited