Tacos are Mexican foods that Microsoft Sam likes to eat. In fact he can't stop eating them. He even goes to the extent of eating other people's tacos. They are Sam's sacred tacos. If you touch his tacos, you will get the same punishment as if you touched his toilet.
In the Season 7 Prologue for nkrs200, Sam wakes up in bed and comments on his big vacation, at which point nkrs (also known as "Boss") says that Sam missed Taco Night. Sam throws a fit and tries to chase him, but winds up getting lost in a hallway. It ends when Bacon was caught trying to show Taco Night 2 to the viewers, and gets dragged to the director's office. Bacon comments on the episode, but Mary prevents spoilers by pressing the censor button. Then the actual episode starts.