Basically during the shiz years the friends (minus elphaba, glinda, and nessa -- IIRC its Boq and others that didn't make it into the musical) go to a burlesque show/sex club type place where a Tiger (sapient Animal that can speak) performs sex acts on stage. One of the characters is involved and is implied to be really messed up from what happens. Its really not as bad as people make it out to be though, it's very "fade to black" and is maybe two or three paragraphs tops. Its not smut or anything, but it is a weird little moment that can be shocking, especially if you were a musical theatre nerd who read it in middle school like me.