1.popes into a volkswagen
随便说下自己的理解，不知道准不准确。
Chandler这句话该是针对Joey所说的，所以有必要看一下Joey的话：
Joey: How do you get a monkey into a zoo?
Chandler: I know that one! ...No, that's Popes into a Volkswagen.
Pope是教皇，Volkswagen是很大众的车，教皇怎么可能屈尊做大众呢？不过Marcel虽然是Ross最亲密的伙伴，也摆脱不了他是只小猴的命运。猴子进动物园是很理所当然的事情，而Joey却问了这么白*的问题，所以Chandler调侃他说了Popes into a Volkswagen.言下之意，Joey你在说什么呢？Marcel不过是只猴子罢了，拜托别弄得他像教皇一样好吗！
Actually, yesterday I asked one of my western friends about your question. According to him, there's no such a punchline in western countries. Apparently, it's just another improvised joke from Chandler. You know how contextual, cynical and dry his jokes could be.
And by the way, my friend also told me some funny fact that in their culture, there is often a joke about "How can you get a ____ inot a volkswagen.... " So, if you really want to mention the original meaning, I think probably this is the original shape of Chandler's joke.

2.Holden McGroin
实际上就是那意思，holding my groin的谐音，外国人造了许多假名字，有的搞笑，有的dirty..

3.'and, my, dead, moher, says, you, are, it'
'it'在这里指代'(the)partner'

4.flame boy，pheo给joey的名字，这个名字给人gay的感觉，下面这个小家伙也叫flameboy

5.my Curious George doll is no longer curious

Season 9 finale 也提过就是一只对什么都很感兴趣，好奇心很强的猴子，Curious George is a children's book written by Margret and Hans Rey.
罗斯养的猴子马塞尔进入了发情期，它冲入瑞秋的房间，瑞秋赶去拯救已经不及，她的“好奇乔治”玩偶已经被马塞尔“欺负”了。“好奇乔治”是一款猴子玩具，因此马塞尔被吸引“干了坏事”。