Perhaps Shorty and Chalky commit identity theft? (9)
I believe the answer is:
nicknames
If this is the answer I cannot explain how the clue works.
Can you help me to learn more?
(Other definitions for nicknames that I've seen before include "Monikers" , "Handles" , "sobriquets" , "Chalky and Shorty, for instance" , "Familiar or affectionate add-on appellations" .)