Newspaper comic strips have always operated in a parallel universe, seldom reflecting the problems of the real world.

No matter what the reader is going through, Dagwood has never had to apply for unemployment benefits; there's no global warming in Mark Trail's forest; and people get old but don't die in Gasoline Alley.

But this Sunday, sharp-eyed readers will find tributes and thank-you's to front-line workers who have spent the last five months fighting the coronavirus and making sure vital services don't stop.

The artists of more than 70 strips will hide six items associated with the COVID-19 battle lines within the pictures - a medical mask, a steering wheel for those who drive delivery trucks, a supermarket shopping cart, apples for teachers, a fork to thank food service workers and a microscope to salute medical researchers.

The idea was the brainchild of Rick Kirkman, who is one of the creators of the comic strip "Baby Blues."

"Every time somebody finds or discovers one of those little symbols in the artwork, to me, I hope that evokes a little bit of gratitude that goes out into the universe," he said.

Kirkman threw out the idea to other cartoonists, and the results can be seen Sunday.

"You can hide these things and just be really devious about it," he said. "You can leave them in the open. You can use them as props. You can even build your gag around them. I don't care as long as they're in there."

But working an apple into a cartoon to thank schoolteachers is not as simple as it may sound.

Sunday comic strips are drawn and submitted to their syndicates sometimes as much as three months in advance.

Bruce Simon is a Berkeley, California-based cartoonist and comics historian.

"The coordination problems are horrific with all these people having different deadlines and the syndicates need to work so far ahead," Simon said.

"Wiley Miller who does 'Non-Sequitur' actually pulled his scheduled strip and did a new one because he works so far ahead. But he wanted to be a part of it so he did a special one for Sunday and the one he had scheduled will show up some other time," Simon added.

And while it's easy to camouflage a truck steering wheel into a 21st century-era cartoon, what about a long-running saga of the fifth century?

"Prince Valiant. Now, how 'Prince Valiant' is going to incorporate a grocery cart or microscope into his historic strip is going to be something interesting," Simon said.

Because no newspaper carries every comic strip, all the strips with a thank-you to front-line workers can be seen after Sunday on the ComicsKingdom.com and GoComics.com websites.