When Rem sleeps the enemy guardian with Naptime in lane and there are no other "awake" enemies around, the trooper wave will walk right past the guardian and continue on to the walker. With a large enough wave and little helpers, they can do significant damage to the enemy walker even a few...
Djinn's mark doesn't trigger Tankbuster or Mystic Burst. It does trigger Spirit Burn and Mystic Reverb. I'm not sure if this is intentional or not.
Also Fire Scarabs doesn't trigger or work with Mystic Vulnerability or Escalating Exposure. It does, however, trigger other spirit damage items...