My children have an interesting vocabulary. Arya will try to say anything you ask her to if she's in the mood to follow directions. Eiley will sometimes repeat the word and at other times she gives this "I'm so cute" look trying to distract us. While they do try to say just about anything, they have their own words for many things. I know I've listed some of them before, but since they are talking more, I want to document more of it.
Cracker= yah-yah
Mommy= me-me
Bunny= me-me (not sure why Eiley uses the same word for me and bunny)
Misti= mih-me
Laine= nay-ne
Chapstick= bah
Pacifier= buh-buh
Salami= mah-my
Ingogh= Ahhh-goo
Sikozu= do-do
Yogurt= rar-ror
Grandpa= Bee-ba
Grandma= Me-ma
Shoe= Do or Jew
Elevator & Elephant are a bunch of tongue flaps with the L sound
I read recently that something like 40% of twins have twin speech. The speech doesn't come from making up their own language, but from mimicking adults and each other. They feed off each others "wrong" words and know what they mean. I would say that some of their words are definitely that, but that a lot of their words are just immature pronunciation of words. I also read that it's typical for twins to have a delay in vocabulary. I wouldn't say that A&E are delayed in their speech, but I do definitely hear other kids their age talking a little more clearly they do. I also hear kids their age who barely string two words together. So, I guess I personally would put them within the normal range for language. I don't think being twins has affected either of them as far as their language goes. Being twins has given them the insight on how to accomplish things that they definitely couldn't do if there was only one of them. They can open drawers that a single child couldn't open. They must have some sort of telepathic communication because they will both stand up, bolt to a drawer, each grab a handle and pull it open without saying a word.