When we are getting into the car, I usually tell Schatz that it's "her job" to sit down in her car seat. Then I buckle her in and off we go. This is our routine and it keeps her from playing around in the car while I'm trying to get her loaded. Sometimes it doesn't work out that way.
Mom: Hop in the car, kiddo.
I got around to the trunk and load our stuff. When I came around to buckle her seatbelt, she was playing in the backseat (not in her car seat.)
Mom: Oh, Schatz, I'm so sad. You didn't do your job.
Schatz: Yes, I did.
Mom: You are not in your seat.
Schatz: You didn't tell me to get in my seat. You told me to get in the car.
Mom (pausing): You're right.
Schatz: Mommy,
I'm very sad. You are supposed to say, (imitating me with a higher pitched voice) "Good Job, Schatz!" (back in a regular voice) You didn't say that.
Mom: Good job, Schatz.
Schatz: Thank you, Mommy.
Schatz sits down in her car seat.
Schatz: You can put my seatbelt on, Mommy.