In the name of the Telly, and the Ernie...
Teaching catechism to the under-two set does present some unique challenges. Toddlers' short attention span and tendency to fixate on a favorite thing, for example, can frustrate many a well-intentioned parent.

Here's how a session went at our house:

Joel: Claire, who made you?

Claire: Elmo

Seriously, though, we are planning to use the PCUSA catechism "Belonging to God" rather than the "Catechism for Young Children" that the PCA uses. This is largely because it uses more concrete language and does a good job of explaining salvation history in a straightforward way. We also like the way it personalizes the material, placing the child in the story of salvation and the church, rather than stating fairly abstract theological ideas.