Evil ab exercise

Get into some version of downward dog (doesn't have to be an especially good one, but do get the spacing between your hands and feet right by getting in a straight-armed pushup position first, then pushing your hips back).

Lift your right leg up in the air behind you. That's your starting position.
Without moving your hands or your left foot, swing your body forward... tuck your right leg in... twist and touch your right knee to your left elbow.
Return to starting position.

Do a few reps on each side.

You can apparently thank my yoga teacher's friend Katie for this one. Damn you, Katie! That's hard!