Castillo has joined the Addicks from Chelsea until the end of the season in a bid to further his development as a player and gain some more first-team experience.
The left-back spent the first half of the season at Championship club Birmingham City but played only three games for them in the league and was recalled to Stamford Bridge and sent to the Addicks.
Castillo revealed that as soon as he heard of the interest from Charlton, he looked up the club’s games on YouTube and was impressed by the fans as well as the atmosphere at The Valley.
The youngster also explained that he looks to command the left flank on the pitch and is fully ready to impress for the Addicks.
Speaking to Charlton’s official site, Castillo said: “I’m really excited and looking forward to working with everyone and playing at The Valley in front of the fans.
“Once I heard that Charlton were interested, I looked at games on YouTube and the first thing that stood out was the fans and the atmosphere.
“I’m a creative player, I like to get up and down the left side and I bring energy.
“I hope that I can develop here and have a successful time.
“I can’t wait to get started and show what I can do.”
The Addicks are currently 15th in the League One table, having collected just one point from their last four games, and Castillo will be hoping to improve as a player in addition to helping them up the table.