My twin boys are usually delightful, but occasionally, my DH and I refer to them as Thing 1 and Thing 2. Thanks to my Dad, we now have t-shirts for them so we can tell them apart when they are in that sort of mood.
I should add that Dr. Seuss has long been a family favorite and even though the boys are now able to easily read to themselves, they often request the we read them a favorite Dr. Seuss book at bedtime.
Who can resist faces like that???