I did know about the link between these two cards:
But I never noticed until now that the Bouffalant is approaching in the background of the Natu artwork. 
EDIT: Apparently @azulryu had already posted this exact same thing 13 hours prior. 
I swear I hadn’t seen the reddit post nor his post. I noticed the Bouffalant in the Natu artwork when I was making my list for the Week #10 Pokédex artworks.
Greetz,
Quuador