Konaki Jijii is basically a bumbling old yokai dude with a pretty effective—if weird—combat strategy: he clamps onto enemies and hardens into stone, getting heavy enough to pin them down completely. He's usually paired up with Sunakake Babaa, and the two of them make a decent team.
The original folklore version is actually a ghost that haunts the woods around Tokushima Prefecture. It shows up as a crying baby, and when some unfortunate traveler picks it up out of sympathy, it suddenly gets heavier and heavier until it crushes them under its own weight. Pretty grim stuff, honestly. The name's kind of a giveaway—it means something like "old man child," which plays on that whole deceptive baby disguise thing.
Content compiled by AnimeList.moe from publicly available sources.