focusing through the glass

Today I went to the zoo with my photography friend to experiment with the AutoFocus Microadjustment feature on our Canons.. She had heard from someone else taking pictures at the zoo that it is possible to preset the focal point behind where the camera thinks it is focusing and thus make the glass invisible. We practiced last night with a grid and tripod so we knew how to set the focus back 1/4 inch (our guesstimate of the thickness of the glass).
Exhibit A is a Mexican Wolf behind a one way mirror. I can see through to him/her, but he/she sees only a self reflection. In the past my shots have been a bit soft, but I think this one captures the eyes quite nicely.
In extras are two other photos through glass. One is a turtle swimming in an aquarium, and the other is a sleeping reptile (yes, I've forgotten the name already) while camouflaged.