Hollywood's Hottest Costumes EVER -- Guess Who! #TBT

Hollywood's Halloween costume parties will be looking like a ghost town this year ... so instead, let's take a stroll down memory lane and try to guess who's behind these sexy costumes!!!

Here's a few hints ... the babe in the Miley Cyrus costume is a hotel heiress. The hottie dressed as Poison Ivy loves to rap about sex. Oh, and the bombshells dressed as Karl Lagerfeld and a Victoria's Secret angel are sisters in a super famous fam.

Check out the gallery for some of the hottest costumes from Halloweens past ... and good luck making your best guesses.