Macaulay's Rep -- Blanket is NOT His Baby

Here's a shocker -- Macaulay Culkin's press agent claims the actor is not the biological father of Michael Jackson's son Blanket.

The ridiculous story, which first appeared in The Sun this morning -- and everywhere else 5 minutes later -- explained how Culkin donated the sperm to create Blanket.

So we contacted Culkin's rep Michelle Bega to ask -- because why not -- and we got the following statement:

"The inquiries are too preposterous for us to even acknowledge."