John Oliver is back, and he’s launched his most challenging investigation yet.

On Sunday’s “Last Week Tonight” on HBO, the comic looked into reality itself, which is under assault by President Donald Trump and a White House that accepts “alternative facts.”

So what can you do when the president himself doesn’t seem to care what the facts are?

Try to teach him anyway ... secretly.

Oliver said he is going to start running ads on some of Trump’s favorite TV shows that look a lot like some of the commercials already airing ― but with a slight difference.

Check it out above.