Does that sound familiar? It should. It's a ripoff of Apple's "Think Different" campaign that irked so many grammarians way back when.
Here's the thing, though. Apple's campaign is better. While it's true that we use adverbs to modify verbs, applying that rule slavishly here undercuts the inspirational message of the ad.
If you tell someone to "think differently," then you're telling him his current mental mode isn't working. Is that a way to sell a product? We think not, unless insulting your customers is your plan. You can probably get away with this with children, who are used to taking orders from adults all day long. Ah, school. Yet another link between fish and kids.
When you're frying bigger fish, though, telling your customers to "think different" is another matter. Here, "different" works idiomatically, if not strictly grammatically. Let's think of another example along these lines: "Think green." You'd never say "think greenly" if you're encouraging someone to think with an environmental focus. Likewise the "buy local" campaign wouldn't mean the same thing if it read "buy locally." The first means buy produce grown in your area. The second means to buy it at a nearby store, instead of online or through a remote catalog.
Our language is flexible enough that you can communicate a big concept with just two words when you know the idiom. If you ignore this, you might end up saying something you really don't want to say, even if it's perfectly grammatical.
In its defense, Pepperidge Farm really is encouraging its little customers to think about things in different ways--if you click to enlarge the photo, you can see that they've laid out fish silhouettes to spell a name and to make a cello. It's a fine lesson for kids, even if "think creatively" or "think imaginatively" would have been the more direct ways of delivering that message.
Meanwhile, we're sending mental instructions to the marketers to "think semicolon" next time. The sentence "Be open minded, what do you see below?" requires a semicolon where the comma stands.