Sure, the observer's consciousness extends to many worldlines, some in which the cat is dead, and some in which it is alive. Then the observer's state of awareness is changed by opening the box. This effectively creates two states of awareness (states of consciousness), each across fewer worldlines, where only one previously existed across more worldlines. It's not the universes splitting, just your sense of awareness or, as some prefer to call it, consciousness.
Where it starts to get weird is when you have two cat boxes, and two observers, both of which can see and even speak with each other, but, neither of which can see inside the other's cat box when it is opened, nor do their poker faces reveal to the other what they see when they open their own box. Then each opens their own box, first one does, then the other, and only afterwards do they tell each other, again, one at a time, what they see. Try to keep track of all the splitting going on.
Fortunately, there is a near infinite number of worldlines. It's kind of like asking how many squares are in a box. It might be limited by the Planck length or something, but that's about it. In a sense, the cat box is the same experiment as the dual-slit experiment, just leaning towards being focused on what we think of as time, rather than what we think of as space.