Hey-
I don't really know much about all this, I just made an account after googling around for info. But I remember years ago people wanted to catalogue the original event Mews on Reddit. I knew I had one, but apparently I have two. (Also yeah, it took me years to finally go through all my stuff and find the cart.)
From what I can remember they were both collected at a Toys R Us in Paramus, NJ. Both are YOSHIRB and on the same Pokemon Yellow cart. I vaguely recall the lady at the register calling someone to bring out the distribution console, and somehow I was able to convince her to give me two. (Or was there some other requirement to get them? It's all pretty foggy at this point. We're old.)
Anyhow, I don't know if this is even important these days, I'd imagine it isn't. But I'll attach pictures since it's still pretty cool. From what I can tell I never actually played the game - I only have 3 Pokemon. That's it. The Pokedex only shows 2 or 3 more, which I'm assuming had to be used for the trade, since they're not on my character and the boxes are completely empty. It's just these 3 guys.
My Pokemon Red cart was pretty empty too. I guess I only actually played Blue!
I have 35926 and 35927 for what it's worth.