She is first seen when Laurie Juspeczyk and Jon Osterman visit Veidt at his Antartica retreat, Karnak. She played an important part in Veidt's life, acting as his sole companion at Karnak. During a visit from Jon and Laurie to Karnak, Veidt remarks that his pet "costs a rather lot to feed."
Adrian's marketer writes him asking if he could add Bubastis and Adrian's fellow masked avengers Nite Owl and Rorschach (along with Nite Owl's ship "Archie" and former villain Moloch the Mystic) to their superhero Action Figures marketing line. Veidt enthusiastically agrees to Bubastis, but rejects the others. He also requests one of the toys of his cat after they are produced.
Bubastis used to sit with Adrian watching television and follows him around everywhere, which she pays for later in her life; while Dr. Manhattan is following Veidt through Karnak, the latter uses Bubastis to lure Jon into an intrinsic field subtractor. Uttering a regretful apology to Bubastis, Veidt throws a switch that incinerates his loyal pet and Jon. Jon then, to Veidt's utter astonishment (though he admitted that he wasn't sure whether removing Jon's intrinsic field again would work), re-assembles himself from the ashes in less than ten seconds.
Assuming he cared about Bubastis - which seems to be the case - it is probable that his apparent calmness was due to the fact that he didn't care who died in the making of his utopia or that he simply shut it out until later.
In the 2009 feature film, Bubastis' body is a light blue-white color but she retains her black striping.