apostrophe
whatshisface
whatshisname
whatstheirname
wastoid
boner-killer
Mack
character
backbite
unreachable
personless
forgotten
son
showee
King Shit of Fuck Mountain
AWOL
excluder
bit player
guv
in one's stead
addressee
cock
compellative
insignificancy
neighbour
nonentity
whosit
you-know-who
dude
fellow
absentee
unfamiliar
buster
empty chair
neighbor
what
holmes
thingamabob
lostling
nonstranger
sideman
Mac
unalive
what's-his-name
you
stranger
answerer
nonreferent
anything
whosiewhatsit
have the advantage of someone
someone
will the real someone please stand up
contributory
musard
unknown
reminder
random
myth
nonresponder
emailee
mamsir
lover
such
anonymous
emailer
moment in the sun
ignoree
addresser
ungainly
singleton
Millard Fillmore
randomer
requestee
brother
amissing
nonkin
nameless
madam
air
hickey
nondescript
happener
castaway
no-name
franker
tag
buddy
absential
stranger in the night
sayee
dingbat
excipient
get lost
Silent Sam