Also don't trademarks get forfeited if you don't enforce them? there are at least 2 of them being misused in this instance.
Edit: not quite sure why my comment is getting downvoted.
Given that the use here is noncommercial (Peng! is not selling a product in Google's area of business), it's almost certainly the case that Google is under no obligation to engage in any legal action. Even commercial parody can be protected, though the criteria are somewhat more complex.
Interestingly, it's easier to legally parody stronger trademarks because of public recognition of the parody - see Louis Vuitton v Haute Diggity Dog for an example. Google certainly qualifies as a strong trademark, although the parody name here isn't as memorable as 'Chewy Vuiton'.
Kneejerk responses.
You're entirely right that Google at least has to legally take some action, as otherwise others can point at the precedent when doing actual attacks on Google trademarks.
And a minor point - "precedent" is commonly used to mean simply "that which came before" but it has a very specific legal definition (generally just decisions issued by a court) that doesn't apply here.