Sometimes such ‘infringements’ are considered parodies.
Copyright law has a parody exception; you cannot act against a copyright infringement when it is clearly meant as a parody.
Trademark law does not have such an exception. However, there is always freedom of speech, that can sometimes prevail above the exclusive rights of a trademark owner.
Suing someone can attract attention. Negative attention. There are cases where, as a trademark owner, you just have to let things go, and wait until it blows over.
As the WWF did with this parody on the diminishing panda population.
DOES YOUR TRADEMARK NEED ATTENTION?
Would you like more information about protecting your trademark?