The Belgium international goalkeeper took in three seasons on loan with the Rojiblancos between 2011 and 2014.
As a teenager awaiting an opportunity at Chelsea, he was offered the chance to star on a grand stage by the Liga heavyweights.
Courtois also took in a Champions League final date with Real before being welcomed back into the fold at Stamford Bridge.
He was hailed as a hero at the time, with his arrival at Aletico helping to cover the loss of David de Gea to Manchester United.
But Atleti fans turned on him when he completed a move to the Santiago Bernabeu in the summer of 2018, mirroring the treatment suffered by Mexico legend Hugo Sanchez after he switched allegiances in 1985.
Ahead of a reunion with familiar faces at Wanda Metropolitano, Courtois saw the commemorative plaque acknowledging his 100 outings for Atleti vandalised with toy rats and beer bottles.
They’ve gone and bought toy rats and put them on Courtois’ 100 game plaque outside the Wanda. pic.twitter.com/o7nnXki5YU— Robbie Dunne (@robbiejdunne) February 9, 2019
Courtois had been expecting a frosty reception from those who once embraced him with open arms.
He was quoted as saying ahead of a derby date: “I expect things will be thrown [at me] for the entire match.
“It’s part of football and it happened to me at Belgium too, but so far this season only one person has shouted at me in the petrol station.
“I will use anything for extra motivation.”
The 26-year-old moved quickly to distance himself from those comments, claiming that he had been misquoted.
He said: “The translation was bad.
“This will be a special match for me because I arrived at the club when I was just a teenager.”
Courtois saw Casemiro fire Real in front on derby day in spectacular style, before Antoine Griezmann restored parity.
Sergio Ramos then converted from the penalty spot to restore the Blancos’ advantage shortly before half-time.