What literary device is being used here?
"reserving first-class compartment for himself and timothy--no one would share a compartment with them--grandfather took him to lucknow where the zoo authorities were only too glad to receive as a gift a well-fed and fairly civilized tiger."

Personification and a surprise ending
The use of "Timothy" implies that Grandfather is merely taking his grandson to the zoo; however, the twist ending is that Timothy is a tiger. Suddenly the reason "no one would share a compartment with them" is all too clear-- no one would want to share a compartment with a large tiger.