They don’t HAVE to be toys either: story books, school supplies, sunglasses, cups, and other items have been packed with kids meals over the years. Debuting in 1979, they’re historically a tie-in to a kid friendly movie or TV series that’s the new hotness. The most famous, naturally, is the McDonald’s Happy Meal Toy.
In common parlance, it’s the toy that comes with a kid’s meal. A Pikachu Gold-Plated Card, still sealed in its bag.