square
lame
noncomprehender
confuter
stranger
nonadherent
enfant terrible
frequent flyer
confounder
Rip van Winkle
unsociable
distruster
know-it-all
birdbrain
know-all
puzzlehead
secret squirrel
obsessor
buffoon
clown
bug
perplexer
bane of someone's life
layperson
creep
merry andrew
goofball
goof
obscurantist
bane of someone's existence
mismeeting
simpleton
the lights are on, but nobody's home
alarmist
mystification
screwball
sphinx
nuisance
experiencer
confusionist
interferer
obfuscation
noncooperator
not know whether one is coming or going
lightning rod
pawn
happener
misappropriator
messer-upper
every shut eye isn't asleep