Nobody can guess what TSR was thinking when they crammed these oddities into the Monster Manual. They ran out of good ideas in the first book and then wrote several more books full of this stuff.
Zack: Be honest, Steve, how many times have you included these in a game?
Steve: I think Keith might have used them one time, but it might just be a bad dream I had.
Zack: They're manta rays as smart as people that tend to be religious vampires. That is conceptually too complicated to throw out there as a random encounter.
Steve: Yeah, I guess you have to build a whole plot around these things.
Zack: You can't just roll some random encounter dice and tell your players, "Alright dudes, you're walking along the beach and you hear some praying. You look over and you see these manta rays in a church. Some of them look really pale."
Steve: "Roll initiative."
Zack: I wonder what sort of religion they follow.
Steve: They're chaotic evil, so it's gotta be a chaotic evil church.
Zack: What was the name of Ted Haggard's church?
Steve: Was he that undead half-elf priest of Vecna from Descent into the Depths of the Earth?
Zack: Yes. That's him.
REFORMED HOG - Former member of the swine family, has now agreed to behave like a proper dog. Free to patient home willing to overlook physical defects. 555-2519
What do you do when The Dark Knight himself pulls a boner?
Available in Large, which is actually a Medium stretched out to appear bigger.
If you're in a tight spot, this is going to be really helpful (I'M JOKING. I'M KIDDING AROUND)
Zack Parsons, Steve "Malak" Sumner, and friends tackle bizarre role playing game products that make them wonder, "What the fuck!?" From the early days of Gygax to contemporary role playing games, none will be spared.