How old is Tinky? It depends if they care to even see the new pet, and I think usually older cats seem to ignore anything new. When I brought my guinea pigs home, we have two 18-year old cats and we just introduced them through the cage bars. I have to say- they could care less! Of course, one cat is blind, but the other just sits and watches them. I recommend spending lots of time with Tinky as well as the guinea pig, so neither feel sort of ignored.