PC1:"Why is there a moose staring into that bush over there ?"
{enemy hiding there}
PC2:"What the heck is a moose doing here ?"
PC1:"Maybe the attacker turned himself into a moose!"
PC2:"It's a shapechanging moose!"
PC1:"I'll cast Charm Person on the moose."
PC2:"I cast detect magic and look at the moose."
DM :"You detect no magic on the moose."
PC1:"It must be a non-detection moose!"
PC2:"Yeah, a shape-changing non-detection moose!"
BWAHAHAHAHAAA!