Mortimer
Appearance
Mortimer is a vaguely humanoid goo person, though being quite a particularly soft and squishy-looking example of his kind. Unless he's moving around or concentrating on holding a shape, much of his mass seems to want to droop down, giving him a half-melted, moist appearance. The goo-man's body is teal in color, filled with some swirls and streaks that are more milky white, making him only semitransparent overall. You can make out some solid shapes within too, many of which appear to be keys. Seems that he's dealt with the lack of pants pockets by simply storing items he needs within his own form.
As he notices your attention on himself, Mortimer pulls himself into a more presentable shape for a moment, with correct human proportions. The smarmy grin on his face and a pompadour haircut complete the image of a human male. Somehow you can't help but feel that he'll try to sell you a used car in a moment.
Events
Mortimer can be found in the Store Everything building that is west, west, west, northwest, and west from the Library entrance. After talking to him twice, and if saying the player will keep his services in mind for the future unlocks the use of the 'Slut Storage' option, where some NPC's that are coded to support it can be brought and kept there, often having special interactions specific to the location.
Currently anyone brought there cannot be brought out, so keep that in mind if bringing someone there (such as Eric who is one of the currently supported options)
Notes
NPC's currently supported to be brought to Slut Storage are Eric, and Dr Mouse (for the last Slut Storage must be 'unlocked' by talking to Mortimer and saying to think about using his services before getting to the main hospital questline where you choose a side, and must side with Dr Matt against Dr Mouse)
GitHub: https://github.com/Nuku/Flexible-Survival/blob/master/Wahn/SlutStorage.i7x