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."