So... inexplicably, someone decided to replace songs on Wikipedia's Year-End 1991 page with Nirvana songs. Looks like it's time to go to a secondary source.
Little did they realized that "Smells Like Teen Spirit" charted a year later in 1992.
That reminds me of one time where somebody vandalized the article for the 2004 Year-End list to make it seem like "Stacy's Mom" by Fountains of Wayne was on there.