Even if your toddler isn't calling the Starbucks guy Daddy, you're likely to come across some errors of overextension as he learns about his world and the many words he needs to describe it. Your little guy might call all cats and dogs "woof-woofs" because it seems to him that cats and dogs are basically the same category of creature (they live around people, have four legs, and are furry). It's also possible, especially as he gets closer to his second birthday, that he knows that cats and dogs are different but just hasn't got the right word yet, or simply can't remember it.
Some ways you can help your toddler along:
Label and explain. Point out things on your walks, in his room, and as you go about your routine ("Good morning! The sun is shining. Do you see the birds outside?").
Read to him. But don't just stick to the story. Talk about what's happening on the page, and ask questions.
Be patient. Don't rush to correct him when he makes mistakes. Learning is a process that involves experimentation and bravery, and you don't want him to be constrained by worries of disappointing you. Just say things the right way, since you're his model for language.