When dealing with babies and toddlers learning first words or children with limited language and vocabulary you MUST think about functionality. What are the words/phrases that are the most functional in this child's world? Is is "penguin" or is it "help"?
Not to say you can't talk about penguins, but to be truthful if your child is not able to communicate basic communicative functions such as requesting more, rejecting, and indicating termination then the least of my concerns is that he/she learns penguin.
Make sure you (and your therapist, if applicable) are also working on a variety of words from different semantic categories. By that I mean not only nouns, not only verbs. Children will usually start combining words when they have 50 words, but they need to have a variety of different types of words in order to do so.
Ok...I'm off my soap box...for now