There are a very popular brand of child’s construction blocks we’ve all played with. The boxes are branded “Lego.”
Now, you see two pieces from one of these sets of blocks on the ground. Do you say
“Look, there are two Legos on the ground.”
“Look, there is Lego on the ground/there are two peices of Lego on the ground.”
In all my life I had never, ever heard or read the term “Legos” until I got on the Web. One piece of Lego was a piece of Lego; collectively, it was a big pile of Lego. To say “Legos” would have been like saying “Deers” or “Mooses.”
So what the proper pluralization? Lego, or Legos?