Like an Old Man Collecting Barbie （きもい）

He Says:
kimoi　（きもい）=disgusting
Young japanese love to use this word to disgusting people or things.
Originally kimoi was got shorted of KImochiwaruI(=disgusting).
Young japanese love to get shorter a word,
like kimutaku=KIMUra TAKUya(japanese famous celebrity name),
pasokon=PErsonal COMputer,
kombini=CONVENIence store.
So young japanese would use kimoi, like when a old guy collects so many barbie dolls or something.
Variations:
Kimo!
Kimo~!
Kimoi!
Kimochi warui!
(all with a frown face,like ugh,blech face)

She Says:
I think that a proper breakdown of how the meaning of the word will help you get a better sense of when you should use it. Kimochii means "feeling" and warui means "bad". So literally this means "bad feeling" and it's generally used when something sort of skeeves you out on the inside...like a toenail that's about to fall off.

The next word is...へたれ。

An Insult in Any Language （まめちん）

He Says:
mame chin　（まめちん）=tiny penis
There is a penis song in which Caneron Diaz and the others sing.
Then they go "Your penis is so big~!!Your penis is too big to fit in here~~!!".
This time,"mame chin" is completely opposite meaning.
Mame means a bean. So it's so small,tiny. If they sang it,like
"Your penis is too small to fit in here~!!".
They say japanese penis are smaller than Americans' in average. Jp guys' penis are said about 5 inches or less.
But mame chin is about 1 inch,like baby size.
If your japanese boyfriend's one were mame chin, please do not say so to your love.
He would be so much hurt by the word from you.
But it would be the best word as a parting shot,"Mame chin!!"

She Says:
I've done extensive research (heh heh) on the myth of the small Japanese penis and I've found it to be wholly untrue. In fact, I would have to say that three out of the five biggest penises I have ever seen in my life have been attached to Japanese men.
Nonetheless, you'll find that Japanese men are totally self-conscious about their size, even if it's normal-sized or huge. And you'll always hear the foreign guys in Japan going on and on about how their Japanese girlfriend said that their dick was SO MUCH BIGGER than Japanese guys' dicks and how they've seen Japanese guys naked in the onsen and can verify that their dicks are small. Well, I've got two little secrets for you:
1. Your girlfriend is bending the truth because she knows it's what you want to hear.
2. Some are show-ers, some are grow-ers dude. And unless you've seen those penises hard, you've got no idea what you're talking about.
I think that telling a guy he's got a small dick is probably a universal insult. Now you know how to do it in Japanese.

This next word is...きもい。

Most Awesome Japanese Use of a Foreign Word （バーコード）

He Says:
bar code/baa koodo　（バーコード）=thin hair like a bar code

Many 50' or 60's years old people have a thin hair like a bar code.
Then subordinates use the word to complain like that stupid bar code boss!
Usually bar code old people's head is a bald head,and looks oily,you know.
So especially many young japanese girls hate bar code guys' looks.
But in a TV show,a japanese girl had to lick a old guy's bar code head.
Then she cried so much,was held down not to escape,and finally,
her face touched the oily bar code head fully.
It was so ugly moment..
That'll be funny if we scan the bar code head,a casher says 99cents or something!

She Says:
Hilarious. This is what we'd call a comb-over. But bar code is such a funny word for it.
There are many foreign words than get incorporated into the Japanese vocabulary and Japan-ized. That's why you wouldn't really pronounce the "r" in bar when you said this.
Usually though, the word just means what it means. This is one of the first words that I came in contact with that had an alternate meaning. And it's a great one!

The next word will be...まめちん。

Instant Coolness in Japanese （なんで やねん）

He Says:
nande yanen!　（なんで　やねん）=Why!
Originally, naze?= why?.
nande yanen is Osakan one, so it's a dirtier or more curt way. But many japanese comedians are from Osaka, and they love to use nande yanen,so it sounds fun for many people.
For example,when you buy a few foods in a grocery store, if the casher says total is "$1 million", you can say nande yanen!.
That sounds funny, because jp comedians use the word for punchline of a joke.
Then many people laugh.
You can definitely get laugh in japan when you say this word, but softly please.If you say it loudly,they feel you are just so angry.
Variations:
dirtiest-nande jya!
dirtier-nande yanen!
normal-nande?
polite-naze? or dousite?

She Says:
I think that this is an example of Japanese humor not translating into English well. For an American, the funny part about the example He used would be that the total was "$1 million" for just a few things. However, in Japan, the funny part is that the comedian responds to this by saying "Why??" I don't why. Or should I say "Nande yanen?"
The one thing I do know is that using this word as a foreigner will make you seem "in the know" and will make Japanese people laugh.
This word is usually said in a moment of incredulousness and in a somewhat whiney voice.

The next word is...バーコード。

A Little Cool （いけてる）

He Says:
iketeru!　（いけてる）=cool!
It's not a dirty word, but slang. We use "cool" many times, in jp, cool is "iketeru",or "kakkoii". So, since it's a slang, only young people use iketeru.
Japanese girl like to use iketeru. If people say iketeru to you, you are cool, but if they say kakkoii to you,you are really really cool regarding your character,sense of humor,and everything about you.

She Says:
Iketeru literally translates to "going to be able to go". I think it's hard to differentiate between various levels of cool and find an appropriate translation. However, I think this one could be translated as "got it going on".
For the record, He mentioned the word "kakkoii" as also meaning "cool". Kakkoii, however is also used by older people. Iketeru is for young people.

The next word is ...なんでやねん。