The most popular comment reminded everyone that Amber Heard starred in Episode 18 of Season 1 and had a particularly steamy moment with Reid.
"I didn't recognize her but was absolutely SHOOK Amber Heard was the famous girl who kissed Spencer in the pool," the comment read.

Amber Heard who made numerous headlines earlier this year due to the much-followed defamation trial against Johnny Depp, played Lila Archer, a Hollywood starlet whose stalker was killing potential threats to her career.

The kiss in the swimming pool happened when Spencer Reid was guarding her house. Suddenly fans no longer find the pool scene hot.

But probably the most mentioned celebrity cameo that shocked fans was the appearance of sweet, dumb Kevin from The Office (Brian Baumgartner) as a ruthless serial poisoner in Season 9 Episode 22.

Seeing him as an unsub really threw me off guard," one of the fans admitted.

Baumgartner played unsub Bill Harding obsessed with Greek mythology and guilty of a series of fatal poisonings. The story of the unsub is truly heartbreaking. When he was a child, Harding and his friend got lost in a winter forest and the friend died before Bill's eyes. 
To help his recovery, one of his teachers gifted him a Greek mythology book, hence his adult obsession. Harding starts killing peopple enjoying their meals at a cafe after he is diagnosed with terminal cancer.