It is no surprise that production sites at times may work differently from dev / stage due to various factors. And in such circumstances, there is a need to login as real site user to be able to reproduce the issue. Of course it is not easy to fix a bug unless it is really reproduced by developer.

In one of my recent works, I found a simple trick using Drush to get access to real user account without distrubing his/her account credentials like login name, email, password, or similar.