Miley Cyrus hilariously proves why Joaquin Phoenix bad at lying

Amid the Joker: Folie à Deux trailer, a video resurfaced that showed Joaquin Phoenix pretending to be familiar with his co-star Lady Gaga but Miley Cyrus called his bluff.

People report the clip is from the non-profit To Write Love on Her Arms in 2010 — in which the Grammy winner was in shock that the Gladiator star did not know about his future fellow actor.

The video took a turn to a more hilarious slope when the Academy winner tried to put a poker face in pretending he was fully aware of the pop icon.

Sensing doubt, Miley puts his knowledge to the test. “You know who Lady Gaga is?” she asks, to which he responds, “Very well."

After his response, Joaquin went a step further, claiming he is well-informed about the A Star is Born actress.

“She has the song ‘Everybody Goes Up.’ She also does the one ‘Two Lashes at a Time,'" the DC star said.

But it appears it was not enough to convince Miley who briefly sang Lady Gaga's Bad Romance to which Joaquin was forced to let the truth out, “I don’t know that song.”