Leonard "Len" Trexler is the head of ODIN. He is voiced by Jeffrey Tambor. Len lives and works in Paris at ODIN Headquarters. His right-hand man at ODIN is Barry Dylan. He is a polo enthusiast and frequently takes practice shots from atop his desk out the upper floor window into the city. Len is one of the three possible fathers of Sterling Archer. While he's still interested in Malory, he was surprised and disappointed to hear how Malory was neglectant to him as a child.
Len was married to Anastasia Trexler, "a tall brunette" woman who only appeared in conversation between Len and Malory in "A Going Concern". She was described as crazy and to have killed herself, making Len a widower.
Although Anastasia could be identical with Ruth Anne Litzenberger because Sterling Archer might not have known her real name and thus dreamed up another one in Once Bitten, which would increase the probability for Len being Sterling's real father, according to the further events in Archer's flashback.
Len often professes his love for Malory, revealing "A Going Concern" that he is willing to marry her despite knowing she only wanted to marry him for his money. His love runs out when Sterling and several other ISIS employees put a Soviet mind control microchip in his head to make him fall out of love with Malory (and unintentionally drive him insane). He is the last known owner of Rabbert Klein.
In the season 2 episode "Placebo Effect", Trexler is present with Malory during the flashback to Krieger's 15th birthday.
Trexler has not appeared in the show since "A Going Concern", visibly driven mad. Despite this, ODIN is still a functioning agency, though it is unknown if Trexler is still head of it. Malory briefly mentioned Trexler's name in "House Call", only to refute any knowledge of him when questioned by her then-husband, Ron Cadillac.
Trexler's design is visibly modeled after his voice actor, Jeffery Tambor.
Archer's paternity has never been confirmed, but Trexler is the only possible father who is still alive. Despite Trexler possibly being his father, Archer was very unhappy with the idea of him marrying his mother.
Possibly codenamed "Z" as ODIN's head was identified as such in "Killing Utne". But this is likely to be a placeholder as Trexler hadn't yet appeared or been mentioned directly.
Jeffery Tambor and Jessica Walter were also on Arrested Development as husband and wife George and Lucille Bluth.