These are the plastic block cat building sets available from JEKCA. JEKCA are modular LEGO-like building blocks from Hong Kong. They’re not LEGO though, they’re just similar. Cat sets range in price from $67 to $87 depending on the style and will almost certainly get knocked off the table by a real cat. Unless you don’t have a real cat, which would make that difficult. You know what my cat knocked off the table over the weekend? Guess. “A vase?” No. “The TV remote?” No. “Playstation controller?” Nope. “I give up.” I don’t have a cat. Just kidding, it was my cell phone and it’s broken now. I made him watch me empty his favorite Fancy Feast flavor into the trash can.

Keep going for a bunch more examples.

Source: Geekologie – Modular Plastic LEGO-Style Cat Building Sets