Leo (Fallout: New Vegas)

Leo is the name of a possibly fictional character mentioned by Lily Bowen.

As it was mentioned by Doctor Henry, Lily is mad, but not dangerous. Leo, however, is all about aggressive and sociopath behavior. When the Courier asks to Lily who is Leo she says that Leo is a very nasty person that always tells her to do bad things.

Leo is very fond of melee weapons and will not be satisfied if Lily doesn't engage in melee combat on every oportunity she gets, if ordered to favor ranged combat over melee or to take a passive stance rather than an aggressive one Lily's reply will be: "Ok. But Leo is not going to like it!"

Lily also tells the courier that Leo was the one that instructed her on making her Vertibird sword using parts scavenged from the Vertibird wreckage on Klamath back at west California.

It is mentioned by Marcus that the Nightkin suffer from schizophrenia induced by their prolonged use of Stealth Boys and during the dialogue with Lily, the Courier may ask about the location of Leo, Lily replies by saying that he's right there by her side, the Courier may then try to convince Lily that there is no one there (to no avail of course). It's very likely that Leo is a hallucination resulted either from Lily's Stealth Boy schizophrenia or from her psychological trauma of seeing her vault invaded by Super mutants, losing her grandchildren, being dipped into the Vats, turning into a super mutant, and then killing so many people while working as a assassin for the Unity.

The creation of "imaginary friends" seems to be common among the Nightkin, Davison takes his orders from a dead Brahmin skull which he calls Antler and Tabitha's radio show is nothing but Tabitha talking to herself and alternating between her own voice and her imitation of the voice of Rhonda.

Another possibility could involve Uncle Leo, a character from a random encounter in Fallout 3.