On February 10, 2014, Tom Cavanagh was set to join The Flash as Harrison Wells. The producers of the show said the following about the character: 'There's obviously more that meets the eye when you see Harrison Wells.... His motivations are a big mystery, and tracking that through has been a very interesting ride with Mr. Cavanagh.' In episode fifteen, Cavanagh was revealed to be playing Eobard Thawne. Regarding this, co-creator Andrew Kreisberg said the character Eddie Thawne served as a red herring so that comic book fans would suspect the latter is the Reverse-Flash because of their same surname without realizing it is actually Wells. Episode seventeen featured the debut of Matt Letscher in the role, which shocked viewers. The executive producers had not planned this twist from the start, with Kreisberg saying, 'We were talking about, 'well what if Wells wasn't Wells? What if he stole Wells' body?' Letscher was offered the role in December 2014, and was cast due to his previous collaboration with Kreisberg and Greg Berlanti in the ABC television series Eli Stone. Cavanagh and Letscher had discussions about playing the character, with Letscher learning how Cavanagh pronounced their character's last name and taking notes by looking at past episodes on how the latter plays Thawne in public and then when Thawne is alone with Gideon, taking inspiration from Cavanagh's intensity and stillness. Cavanagh would continue to primarily portray Thawne on The Flash, while Letscher subsequently played a time-displaced version of the character on The Flash and Legends of Tomorrow.