Kim Kardashian's famous backside made an early appearance on the 50th anniversary special for "Saturday Night Live" ... with Kristen Wiig pretending to smack on her behind like bongos.

In the first sketch after the monologue on 'SNL50,' Kardashian appeared as one of the Maharelle Sisters -- the singing quartet with three gorgeous sisters and then Dooneese, a character played by Wiig with a huge forehead, tiny hands and a nasally singing voice.

In this particular version, Will Ferrell -- playing Robert Goulet -- is on "The Lawrence Welk Show" trying to find choose between three women Ana Gasteyer, Scarlett Johansson and Kardashian ... but, Dooneese keeps getting in the way.

Hijinks ensue ... and, Kristen ultimately ends up turning Kim around and pretending to smack on her butt -- a moment which carries on for quite a few seconds.

Ultimately, the sketch goes on from there ... but, it's certainly attention-grabbing -- and getting some mixed reactions online.

As you know ... Kim hosted 'SNL' back in 2021 where she connected with Pete Davidson -- kicking off their 9-month-long relationship.

Pete's in the building tonight too ... not surprising given he's an 'SNL' staple. The two even hit the same party Saturday night for Chris Rock's birthday -- unclear if they chatted once inside though.