So, from what I can gather here, these "characters" (and I use that term loosely) were used in Scribblenauts and then a year later, they had trademarks filed for them? I'm no expert in these matters, but it sounds to me like these individuals may have thought their trademarks would be retroactive and as such they could claim the big bucks for this infringement.
Also, I'm guessing that no, you couldn't use Bugs Bunny in your game just because he appeared in a meme because well, he's Bugs Bunny. How many other pre-existing fictional characters have appeared in memes: Adam Jensen, Neo, that girl from Bleach with the leek, Kirk, Picard.... Would you use any of those in your game just because they appeared in a meme. Unlikely. You can hardly look at Nyan Cat and Keyboard Cat in the same way, as they were likely never existed before their memes.
Be sure to update us when these claims crash and burn in a predictable but nonetheless entertaining manner, will you?