Sam and Dean's Initials

Sam and Dean carving their initials into the Impala from 5.22 Swan Song

Sam and Dean's initials seen in 11.04 Baby

Sam and Dean engraving their initials on the library table in 12.18 The Memory Remains

The engravings on the library table with Mary's added by 14.18 Absence

When they are kids, Sam and Dean carved their initials into the Impala. They are seen in flashback in 5.22 Swan Song and 11.04 Baby.

In 12.18 The Memory Remains, Sam and Dean sit in the library wondering what their legacy will be a hundred years from now. Sam suggests the people they saved will be their legacy, because they left the world better than they found it. Dean wonders about the bunker, if other hunters will move in. Dean gets out his knife and he and Sam carve their initials into the library table as they had done in the Impala. Later in 14.18 Absence, we see that Mary Winchester's initials have been carved alongside Sam and Dean's initials.

These carved initials were used as a design element at the 300th Episode Party.