LOOK: KATY PERRY FANGIRLS OVER MARIAH

Fangirling! Katy Perry stopped by Caesars Palace on Sunday to watch one of her idol's final shows before her residency -- Mariah Carey. (Mariah #1 to Infinity closes on July 26.)

And she shared it on her IG.

Look:

moments.

A video posted by KATY PERRY (@katyperry) on Jul 20, 2015 at 12:29am PDT

MORTA 😩 LINDA 😩

A photo posted by KATY PERRY (@katyperry) on Jul 20, 2015 at 12:55am PDT

"MORTA LINDA" translates to "dead beautiful."