Here's a few off the top
Typical DD line: This is the BEST coke you'll ever see
I am constantly amazed how often this line is used (and often genuinely believed by DD) Just how is one expected to believe improvement is possible when the first stuff they tried to sell ya was said to be
"As close to pure as you can get"
Cocaine cures everything
This came from a CNS report on an old doctor in the US who had several long cotton buds sticking out his nostrils. The show interviewed his patients, who also had the cotton buds in full operation. It looked painful, 6-10 things jammed up there. But anytime symptoms of their complaint arose, or their nose got sore, a simple twiddle of the sticks released more cocaine and they were on there way to good health 8)
Fosters Beer method of making LSD
This was initially supposed to be a joke but it wasn't long before people were spreading it as gospel. Not until the first LSD faq came out on hyperreal was it dispelled as the BIG joke it was. Even funnier was to read accounts of people who said they'd actually done it...hee... hee....
As a person gets older, they grow out of pot
mmm.....still waiting for this one 8)
MDMA makes your hair grow!
A locally sprung notion of a balding friend who reckons MDMA has made new hairs sprout. Imagine how funny it was to hear Paul Dillon state it was found to do the opposite - MDMA makes your hair fall out !!
...I just don't know whether I've got the heart to tell him
MDMA can be made from piperonyl butoxide
You'll find this in pyrethroid based insect killers. The butoxide is present as a synergist. It CANNOT be used to make MDMA
Hanging mull when drying makes the resin drain from the stems to the heads
It's been proven many times there is little if any vascular movement of THC. Therefore there is none to travel. The plant will dry slower usually improving taste and appearance, which is often interpreted to be more THC