The Neko Neko no Mi, Model: Saber Tiger is an Ancient Zoan-type Devil Fruit that allows the user to transform into a hybrid and full version of a saber-toothed tiger at will. It was eaten by Who's-Who.
Sāberutaigā (サーベルタイガー,Sāberutaigā?) is a Japanese way of referring to the saber-toothed tiger, loaned from the English "Saber Tiger" (though the latter is not used in English).
Strengths and Weaknesses
A user of this fruit's power can turn into a smilodon or "saber-toothed tiger"—a powerful, predatory big cat from prehistory that is known for its signature elongated, curved fangs on its upper jaw. The ability's current user Who's-Who, who is an already large man, grows to very notable size in his full Beast Form, dwarfing his human-sized subordinates and a 3m-tall fish-man.
No weaknesses of the fruit's power are known beside the standard Devil Fruit weaknesses.
Who's-Who was first shown in his full Beast Form relaxing at the "Nekoka-fé" in Kaido's fortress. In combat, Who's-Who's long, sharp smilodon canines seem a potent weapon.
The saber-toothed tiger (correctly named Smilodon) constitutes the best-known genus of saber-toothed cats and is, overall, one of the most famous prehistoric mammals. Despite its popular name, it is not closely related to the modern tiger or, for that matter, any extant feline.
It is theorized that the Smilodon actually possessed a short, stubby tail, unlike modern large cats as well as Who's-Who's transformation, which respectively bear long tails.
Smilodon have been artistically restored with plain coats (like Who's-Who's) as well as spotted ones (seemingly the ancestral condition for feliforms), both of which are considered plausible.
Befitting his Devil Fruit ability, Who's-Who's closest subordinates appear to follow a cat theme, including several feline SMILE users.