When we have collective nostalgia for the ’90s, we’re usually remembering songs, fashion, film, TV shows – things that were formative in the best ways: “Let’s Talk About Sex,” flannel, Clueless, Twin Peaks. But alongside the pop-culture touchstones, those of us who lived through that era were also shaped by some decidedly ickier historical moments: Girls Gone Wild, breathless countdowns to Britney Spears’ 18th birthday, R.