A pathological liars, or "mythomaniac". A
person deluded, believing in a world which they created, where anything no matter how idiotic or absurd, is possible.
Alternatively, a
person so utterly inept, moronic and borderline
retarded they unable to perform the most basic of tasks.
"I ran 8
miles in 6 minutes today!"
"Dude, don't be such a Waller!"
"I used to be famous in
America, I was in a band you might of heard of: Metallica!"
"
Wow, you're an immense Waller."
"Count to 10? 1, 2, 6, 8, 10. Those other numbers don't matter."
"You Waller, get out of my sight, your Waller-ness disgusts me."