Toys with interlocking pieces (ex. Mr. Potato Head).
Putting Salt into Cholent, Soup, Etc., and Pieces of Radish, Onion, Garlic, Etc.: Eating Right Away;
understanding the difference between tying and sewing in halacha;
Other issues to watch out for when food, wax, etc. is attached to the part where there is no letters, numbers, etc.