The Alternateville Horror - S4-E8
Stupidity: Colin tells the group he saw a ghost (a non-corporal shade) who walked through the door. They laugh at him and blame it on what he was watching on TV or too much sliding. Given everything the group has seen, vampires, a dragon, etc, they should have least checked it out. Quinn himself was once on the astral plane and nobody could see him except one girl who thought she was seeing a ghost, and he could walk through solid objects.
Data World - S4-E17
Stupidity: One of the hotel rules is "no singing in public places." Rembrandt ignores this and starts singing, despite pleads from the bartender. The group is already questioning how they got inside the hotel, why there's no charge but nothing is free, and Rembrandt even wants to know what the hell is going on. Rembrandt has been on enough worlds to see what happens when people break the rules. It's stupid for him to start singing in a place he knows nothing about as if this rule didn't apply to him.
