Duplo blocks are made by the Lego company. They are like legos, but bigger and chunkier (less swallowable). Like this:
Amanda R. captured this screenshot on the Duplo website:
Apparently, if you’re going to buy Duplos for some little kid, the very most important first piece of most vital information you will ever need before you ever ask anything else is whether or not the kid has a penis or a vagina.
Meanwhile, Elisabeth R. found exactly the same thing at the Toys R Us website: