Patrick McDonnell is best known for his daily strip Mutts, which runs in over 500 newspapers thru King Features Syndicate.
Before starting Mutts, however, he did a monthly strip for Parents magazine called Bad Baby, which ran from 1984 to at least around 1997.
The local university's library has a bound copy of a bunch of magazines, Parents being one of them.. I xeroxed some of the Bad Baby strips here.
Unfortunately, these are all in black and white; they were originally printed as is from Patrick's watercolor, so you're not seeing everything here.