Pat the Bear is a character from Hop on Pop (or at least that is what they call him). He appears to be related to Pop and his obnoxious children. Pat is either not very bright or has some kind of compulsion to sit on things that are not meant to be sat upon.
This is not so much of a problem when it's a hat someone probably left at Pat's house after a party or something. But the cat he attempts to sit on appears to have a strongly negative opinion about his attempt to sit on him, and in spite of Pat's apparent satisfaction in the illustration, most people would probably not enjoy sitting on a baseball bat because Pat's method defies the laws of physics. As for the cat, Pat tries to sit on him. And the cat, he meows loudly. (The cat in this book is possibly Pat and his brother's pet cat.) The cat, he does not appreciate Pat sitting on him.
Pat's most problematic seating choice comes when he attempts to sit on a cactus, which he fortunately is warned away from by a younger but wiser bear, perhaps a relative. (This is possibly Pat's younger brother.) This is a poor choice not only because it will hurt his bottom, but also because "cactus" does not rhyme with the words hat, cat, and baseball bat. The younger bear's rhyme about the cactus (as stated in the book) is, "NO, PAT, NO! DON'T SIT ON THAT!". However the word "that" most definitely rhymes with the other three words (hat, cat, and baseball bat).