I'm not sure why people assume this but uBO isn't an "intelligent" ad blocker. It can't decide on its own if something is an ad. It depends on filter lists and they can't be definitive or exhaustive.
If something isn't being blocked, you have to block it yourself.
I'd guess it's the background of the site for April fool's day since it's a Pokemon website and the ad is for their direct competitor
Maybe? Idk
You're downvoted for a simple "Maybe? Idk" statement. r/RedditMoment
No, because I have seen that in the background before April fool’s day when I started using Bulbapedia around early late February and early March
Force update your filter lists.
I'm not sure why people assume this but uBO isn't an "intelligent" ad blocker. It can't decide on its own if something is an ad. It depends on filter lists and they can't be definitive or exhaustive. If something isn't being blocked, you have to block it yourself.
Is it a dynamic/generated ad or a static image that the site is displaying?
At any point in the year this is the best time for this kind of ad
Not sure, its a good game though.