SQL Server caches the definitions of temp tables and table variables, to reduce the load on the system catalog in tempdb on busy systems which creates a lot of temp tables. Typically they have a name that starts with # and is followed by eight hex digits. –Erland Sommarskog
SQL Server Temporary Table Caching
This tip will describe the condition to allow caching of a SQL Server temporary table and a demonstration to benchmark the performance between a cached vs. non-cached temporary table.
Source: www.mssqltips.com/sqlservertip/4406/sql-server-temporary-table-caching/