Sanhedrin 65b
Yes, of course. Rashi on the daf too is well known.
It was a dream.
And of course, the story from Rav Chaim Volozhiner is a straw man story, literally. The story of the Maharal was concocted a bit over 100 years ago. It never happened, but it sure is good for business.There are other similar legendary stories, all legendary.
This issue has been discussed off and on for some time. A golem is impossible to create because humans cannot create yesh me’ayin. Allegories, meshalim, dreams, hallucinations, concocted stories for educational purposes, all are possibilities. But actual? No.