I'm from German decent.
What is Erev Rav.
"What is Erev Rav."
Depends on who you ask.
After the Jews received the Torah, Moses went up Mt. Sinai for 40 days. After according to an erroneous calculation the 40 days had passed, many of the Jews believed that Moses had died and they needed a new leader. The Erev Rav (most consider them a group of Egyptian pseudo converts who maintained their idolatrous beliefs) made the Golden Calf. Many Jews sided with the Erev Rav. The members of the tribe of Levi did not.
According to the Ohr HaChaim, they were spies sent along by Paroah to sow seeds of dissension among the ranks of Jews. They were the rabble-rousers, and, though, they may not have been successful at making the Jewish people return to Egypt (which, they came close to doing), they were the cause of Moshe's failure to enter Eretz Yisroel, and the delaying of the Final Redemption.
Regardless of origin, they have always represented one of the biggest stumbling blocks in the path of the Jewish nation, and I believe their descendants --- literal and actual --- are among us today.
But, hey, I'm a cohen, so I can judge. :)
(Not really, we all have erev rav in us. Me moreso than most.)