Wham!'s classic carol appeared on the Hot 100 for the first time two years ago, reaching a prior No. 41 high. As for why it didn't chart on the Hot 100 upon its original release, it was not then available as a commercial single in the U.S., and, per chart rules at the time, was ineligible for the Hot 100 (although it was released elsewhere in the world and charted in other countries). In the digital era, the track was made available for purchase as a download and via streaming platforms. (It was finally released as a physical single in the U.S. on the Black Friday edition of Record Store Day in 2014 as a 12-inch vinyl single (in red and green) in honor of its 30th anniversary.)
More chart fine print: Even if "Last Christmas" had been a commercially-available single in the U.S. when it was first released, it likely wouldn't have hit the Hot 100. As chart historian Joel Whitburn notes in his book Christmas in the Charts, "From 1963 through 1972, and from 1983 through 1985 [with minimal exceptions], Billboard published a seasonal Christmas Singles chart and did not chart Christmas singles on the Hot 100."
Per current Hot 100 rules (in place in recent years), older songs can rank in the top 50 if experiencing significant multi-metric resurgences, and multiple venerable holiday songs re-enter or debut each season.
Before Wham!'s original "Last Christmas" reached the Hot 100 in 2016 (the year that George Michael passed away that Christmas Day), two versions of the song had hit the chart: the Glee Cast's cover, which reached No. 63 in 2009, and Ariana Grande's (No. 96, 2013).
Among other versions of the song, Taylor Swift's 2007 cover hit No. 28 on the Hot Country Songs chart that holiday season.
Wham! (Michael and Andrew Ridgeley) adds its seventh top 40 Hot 100 hit and first in over 32 years. The duo had last reached the region with "The Edge of Heaven," which hit No. 10 in August 1986. The pair's first six top 40 entries all entered the top 10, with the first three all ruling at No. 1: "Wake Me Up Before You Go-Go," "Careless Whisper" and "Everything She Wants." "Freedom" and "I'm Your Man" then each hit No. 3.
Additional reporting by Alex Vitoulis