How does one see Kel'Thuzad's prized kitty? Quite easily!
When playing against Kel'Thuzad, if you play Animal Companion, Kel'Thuzad will summon his kitty for you instead of one of Rexxar's beasts.
Old Gods Update: Call of the Wild summons not only the three normal animal companions but also Mr. Bigglesworth!
Kel'Thuzad will not directly attack Mr. Bigglesworth.