If you say Duck, and the next person says Goose, you have to stick your finger up your butt.
If you say Duck, and the next person says Duck, you are safe

If you say Goose and the next two people say Duck, you have to stick your finger up your butt
If you say Goose and the next two people say Goose, you have to stick your finger up your butt
If you say Goose and the next two people say different things, you are safe

I will start:
Duck