John Oliver is giving credit reporting companies a taste of their own medicine.

On HBO's "Last Week Tonight," Oliver found that a quarter of credit reports have a mistake in them, and 1 in 20 have serious errors -- including cases of mistaken identity.

Consumers have in some cases had to fight for years to prove they're NOT another person (or in some cases, that they're not dead); and all the while, these errors can make it difficult to buy a car or a home, get a job or even rent an apartment.

So what's it like to be mistaken for someone else?

Oliver gives the three biggest credit reporting firms a hilariously crude lesson in mistaken identity.

Check it out in the clip above... and be sure to visit the websites of TransOnion, Experianne and Equifacks.