Below are some variations of visual quotes.

In this version I used an image of a fist ripping through the paper to imply seriousness. I have  sketched the word “serious” onto the knuckles of the fist to resemble a typographic tattoo.

For the second version I used the image of laughing/smiling masks on black background.There are two ideas here one being that each joke has a little bit of truth in it so when one is joking, one is in part relaying the otherwise “uncomfortable” truth. Joke allows for the truth to be expressed. Another idea is that in order to make a good joke, seriousness and insight is required, otherwise the joke is flat.

The third version plays on the meaning of the words and its opposites. Hence the word “serious” is displayed in whimsical fonts. I have also used outlines for the rest of the copy to minimize its impact and throw the attention onto the word “serious”.