Just had our 18-month checkup
From most babies, I think you can expect a lot of resistance. This appointment is in the height of a toddler's early self-control stage, so babies really hate being held and poked and prodded.
The doctor will do a general check of ears and eyes, back and feet, and the under diaper area, just to make sure things are growing properly. We also received an early screening test for the autism spectrum by answering questions about development and engagement. She was weighed, and her height and head circumference were measured and compared with averages to ensure that growth is trending along the same curve. Finally, we ended our appointment with a single vaccination--Hep A. Our pediatrician says that this is the last vaccination until she is 4, though, and we're following the standard CDC schedule.
It was pretty good overall!