I really regard this as one of life’s great mysteries.
One thing that everyone I have ever met seems to agree on is that the dress worn in the prom scene of Pretty in Pink is hideous. Just, deeply hideous. It doesn’t matter your age, your background, your personal taste, we all know this dress is awful, right? Right. I’m continually torn on whether or not this was intentional, though. Here are two ways of thinking about it:
1) Look, 1986 was a time when people were really experimenting with fashion and going against typical rules (like redheads wearing pink!). The deliberate Reagen-era old fashioned neckline blended with futuristic details like the shoulder cut-outs seem to indicate that this could be seen as a pretty cool dress at the time. Or at least, the kind of cool dress that might be made by someone in high school who would ultimately become a fashion designer. You can say it’s horrible, but Jesus Christ, have you seen what Molly Ringwald wears in all John Hughes movies? It was just a product of the period. It was cool for that very specific period.
2) Okay, no. John Hughes, the costume designer, or whoever was at the wheel of this crazy ship, knew that dress was hideous. But it’s supposed to show that unlike the other girls at Prom, Andie isn’t so much invested in looking appealing to other people so much as she’s interested in knowing who she is. The dress is a combination of her boss’s old gown from her cool job at a record store, along with what her father gave her, plus her own well honed sewing skills. The fact that she prioritized those things over looking “pretty” is what makes her admirable, and this reflected that. This ugly dress is being worn to show what a good person she is.