Their commentary is not always funny, but the illustrations from yesteryear sure are.
Just take a look at the “Owlbear” from the first edition of the Monster Manual. It’s a hybrid between - you guessed it - an owl and a bear. And he’s a “ravenous eater, aggresive hunter, evil tempered at all times”. Next time you play an RPG, you better watch out for those Owl Bears, because they are mean SOBs. Not to forget the Thought Eater and IXITXACHITL, both monsters of such horrible proportions they will redefine your notion of absolute fear.
I don’t think it’s all crap though. The illustrations may seem cheap, but they’re lovingly cheap. Like someone was really scared of meeting a Thought Eater in the dark. Or scared they wouldn’t get paid for their illustration. Who knows. Check out Monster Manual Part 1 and Part 2, as well as Deities & Demigods, the Tomb of Horrors module and the non-D&D Rifts Core Book for more zany art and tales of the unordinary.