Sue Markham got the ultimate case of puppy shock when she thought she adopted a Jack Russell terrier — that turned out to be this monstrous Mantle Great Dane.

The English grandmother of four wanted a small pup, since her hubby told her he absolutely didn’t want a “big dog.” A Jack Russell would be perfect, since the breed doesn’t get heavier than 18 pounds.

She instantly fell in love with Yogi, who at the time tipped the scales at just under 2 pounds (inset).

But Yogi kept growing, gobbling more than $60 in food a week and ballooning to 210 pounds — one of the largest dogs in the United Kingdom, according to Mercury Press.

Now nicknamed “Bear,” the 6-foot-10-inches long Yogi wears a horse coat when he goes outside to romp in the Markhams’ back yard.

As puppies, Mantle Great Danes can closely resemble terriers, as the Markhams discovered.