There is a line in the movie Casino:
No matter what the Feds or the papers might have said about my car bombing, it was amateur night, you could tell. Whoever it was, they put the dynamite under the passenger side. But what they didn't know, what nobody outside the factory knew was that that model car was made with a metal plate under the driver's seat. It's the only thing that saved my life.
I understand the phrase to mean amateurish here. But is this phrase amateur night idiomatic? Is this usage common? With few sources having pithy words about this term, it seems a very uncommon term.