As mentioned in today's review, here is the evolution of the Owlbear's art.
As a reminder, here's the random drug store toy that inspired Gary Gygax to create an "owl bear":
And here, from the 1975 Greyhawk supplement, is the first published art of the creature:
Quite a departure! You'd never know that was based on anything. However, the 1977 Monster Manual was much less creative:
We're all agreed, that's obviously a kappa, right? Well, maybe, maybe not; a lot of the "Prehistoric Animals" monsters sold in those bags of toys were based on the monsters that fought Ultraman. None of Ultraman's official enemies match the owlbear's inspiration, but (as ridureyu said down in the comments) there are magazine illustrations of fan creations that do look similar:
No original toy has ever surfaced that this knockoff might be copying, so it's possible the Hong Kong company, casting about for things to pad its numbers, paid to have its own creatures made, using a magazine like that as a source for designs. Meaning the grandfather of one of D&D's most famous creatures could be some unknown otaku's kappa-influenced OC.