English not being my native language, LOTS of them, although I got a whole lot better after living here for a while.
Things would get a little crazy when we would cover songs and I had to figure out the words - before the days of internet, and without anyone who natively spoke English to help, if they weren't printed on the sleeve, I was left to figure out what I could and extraoplate the rest. Which was embarassing, but, I had to sing something...
I remember reading a John Lennon biography in 1990 and the author was saying that in the early days, when Lennon could not understand the lyrics of a song they were covering, he would just make up his own (sometimes completely absurd). That was then end of my complex. The things I sang (and mumbled) on stage from that point on, man... lol
Oddly enough, maybe because Diary of a Madman was the very first album I ever bought and it had the lyrics printed on the sleeve, I developed a knack for understanding Ozzy's lyrics. I was fluent in Ozzy before I was fluent in English.