He's has a mean stare but usually crack's jokes
Good luck on your mission and guard your backs folks

from Eminem – Backstabber Lyrics on Rap Genius

Meaning

He can look mean and what not but he’ll crack jokes so that way he can appear friendly and not come off as bad. But he is, so don’t be fooled by his charm, and remember to guard your own backs or you’ll be stabbed yourself.

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