Translation:This child and this cat run in this direction together.
Accepted 2019 as "this child and this cat".
In English if the two things are near each other, we often use "the/this/that" and their plurals only on the first.
When we know which things we are talking about:
The cat and mouse are playing games. The cat and the mouse are playing. These roses and daisies grow quickly.
......... When we need to be specific because there are more choices:
The cat and the dog play games. The cat and that dog play. These roses and these daisies grow quickly. That rose and this daisy do not grow slowly.
"[…]part and counterpart wandered independently about the earth in the stupidest manner for a while, till the late time came." — Thomas Hardy, Tess of the D’Urbervilles, 1891.
@Jaggi.licious is right. "Stupidest" is a word and has been used for decades. Also, although this sentence can be used to help learn words and sentence structure, that doesn't mean it can't also sound silly. Those two things aren't mutually exclusive.
More sources backing up that "stupidest" is a word: