These are on a playschool DVD which we have had for years so that's how long i've been wanting to make them! Playschool is one program I can sit and watch with my kids. They have a great site that has lots of useful box ideas and some recipes, check it out:)
Spread vegemite (or promite, marmite) on rectangular shaped crackers. Then top with half a cherry tomato, a small chunk of cheese and then a small piece of gerkin. My son didn't like the gerkin but use whatever, a piece of lettuce or something.
Little Chefs crackers. She's known her traffic lights since she was two! lol