Good slogans are memorable; great slogans are unforgettable. Numerous companies have used slogans that aren’t a statement, rather a question such as Klondike’s “What Would You Do For A Klondike Bar?” Verizon’s “Can you hear me now?” and the California Milk Processor Board’s “Got Milk?”

While the original Klondike campaign in 1982 featured the jingle that no one could ever forget, 30 years later that slogan has almost turned into a game, resulting in many funny (and sometimes offensive) viral memes.

Verizon’s ad had viewers asking themselves, is my service that good? One question raised numerous questions about their phone carrier. And if you’re questioning your service, Verizon’s done its job.

And of course there’s the most famous of them all: “Got Milk?” The “Got Milk” slogan has been used since 1993. Used in juxtaposition with celebrities sporting milk mustaches, the California Milk Processor Board made consumers not only wonder if they had enough milk in the fridge but also sparked a tidal wave of spin-off apparel featuring the commercial font and “Got (insert item here)” across the chest.

Slogans using questions can be powerful, particularly if they’re open-ended. If an ad asks you a question and you’re still thinking about it after the commercial’s over or you’ve turned the page, mission accomplished.

It’s important to be wary, however, when it comes to yes-or-no questions. Though “Got Milk?” pulled it off, in general asking a yes-or-no question can give the audience the opportunity to say no and turn the page, change the channel, or zone out. This happens more often when brands use questions as headlines instead of taglines, like in this ineffective bus shelter poster:

If you’re considering using a question as your slogan, be sure to think about what the potential responses could be; the more (positive) discussion it creates, the better.

And whatever you do, don’t force it. The most important question of all is: Will this work for my brand?