If you look at the court filings linked elsewhere in this thread, it isn't as simple as just a slogan. They copied the trade dress to the point that the truck looks like a Kelloggs waffle box.

Trademark law does have carveouts for people that are selling different products, doing parody, etc. But that isn't what this is.

There are carveouts for things like parody and fair use, but running a restaurant that uses wordplay of a very specific marketing phrase, the same colors and fonts, and branding is the issue.

If you go look at pictures of the truck, the business branding, and other things it is very clear why Kellog’s has a good argument that their trademark is being used in a way that could damage the brand, or confuse consumers.

Not relevant to those who have to act on the law as it is today.