We got the approach of talking to her whatever feels right.
I mostly talk English though is not my maternal language but I do say phrases in Greek language to her, also use Skype with my parents, Greek cartoons, the fisher price puppy like you do.
I took the advice from a friend that specializes in multilingual kids.
The approach a parent speaks exclusively one language works best if you have great everyday exposure to this language. As we don't have that we use all three languages at home and eventually everything will click in place when she is older and we go for vacations in Greece etc etc.
I think you should relax and explain when your Little one asks what that means in whatever way you can. After all they have to make the connection that dog is dog in whatever language and he will eventually speak them both when he chooses too, line when you go back home for a trip and he speaks to other kids in Lithuanian.
Good luck it's hard work but it will all worth it the trouble.