Lachlan Watson influenced Theo's "queer journey". In the original script, the character was supposed to came out as transgender in the first few episodes of Part 1. After conversations between Roberto Aguirre-Sacasa and Lachlan, writers decided to develop the character's journey to a slower pace. 
The major transition steps were moved to Part 2, starting from using masculine pronouns and naming himself Theo, after his ancestor Dorothea Putnam.
The role Lachlan Watson got cast for was under a completely different name. An hour after Roberto Aguirre-Sacasa got their tape, the two of them discussed Lachlan's entire gender journey on Skype. A week before production of Part 1, the character was rewritten.