The gizmo effect

The phenomenon of moving from a topic of deep intellectual stimulation to one that is much lighter and playful (alright...stupid).

Example:

Breakfast Bagel Eater 1: "But I think that's the real reason why separation of church and state is so key"

Breakfast Bagel Eater 2: "Actually, I disagree."

Breakfast Bagel Eater 1: "Really? Why?"

Breakfast Bagel Eater 2: "I mean if you think about it, the real reason is because your mother doesn't love you."

Breakfast Bagel Eater 1: "Yeah, well your mother sure was lovin' me last night! Ohhh!"

Note: It can also start out silly, and end up intelligent.