No, it's not. "Lego" was never intended to be a countable noun. It's like "milk" or "water" in that there are only very specific circumstances that allow for pluralisation, and the usage in the comic isn't one of them. Although, yes, it is a brand name. I'll come back to that.

One country in particular, however, has decided that it is a countable noun, and so a lot of people grew up hearing it used as one, so they have very strong feelings about it when they're told it's wrong by people in countries who despair every time they hear it.

But here's the thing, brand names work like uncountable nouns. Would you refer to your groceries as "s"? What if they were all store-brand items? e.g. "In these bags I have my Walmarts". If that sounds odd, that's how using "Lego" that way sounds to people who don't.

If you do do that, I'd be curious as to what parts of the world do that for multiple brand names, whether or not "Lego" is amongst them.