In 1986, reruns of the live-action Dennis the Menace were airing on Nickelodeon's Nick at Nite schedule, and sometimes on Nick itself. Someone at DIC and/or the Program Exchange, which handled the distribution, must've seen the ratings and decided it was way past time for Dennis to return to television, this time in an animated series.
This version of Dennis the Menace lasted a couple of seasons, airing weekdays, but unless you were a fan of the Hank Ketcham comic strip and its accompanying line of comic books, published by Fawcett until the 70's, then revived by Marvel briefly in the 80's, you probably forgot about this, since 1986 to cartoon fans was largely the Year of the Ghostbusters, with two competing series debuting that same year, including one produced by DIC (in conjunction with Sony) based on 1984's "Ghostbusters".
For Dennis, DIC's art staff came up with a faithful adaptation of the strip, right down to the character designs. For what it's worth, DIC brought Dennis back in a weekly series a decade later, airing on CBS on Saturday mornings that lasted about the same length of time. If memory serves me correctly, Dennis replaced Inspector Gadget on DIC's 1st run roster.
Here's the episode, "Dennis' Yard Sale":
One wonders if Ketcham got his inspiration for the strip from Hal Roach's Our Gang, aka The Little Rascals. Dennis was a 1-boy gang by comparison. He meant well, but was just too over-eager.