Busted!

This is Simon attempting to convince me that he wasn't just trying to get behind the box fan to sample its vintage 1950s wiring.  He had it on good authority that this rare delicacy is absolutely to die for because its crunchy center tastes like purple.  (Don't worry, he had no chance of actually succeeding in his gastronomic quest.)

Nothing to see here!

Situation is normal and everyone's behaving.  Uh, just ignore those digging noises coming from behind me...it must be a problem with your ears.  Um, yeah.  So, how are you?

Busted!

This is Simon's "guilty/I'm a bad accountabilibunny" face.  I know that either he or River is up to no good when he looks like this.

And this time it's River with her "I'm in so much trouble right now" face.
Other potential captions for this look are, "Yes, this is exactly what it looks like I'm doing," and "How does she always know?!"