Lady Gaga thought Isla Fisher was Amy Adams.

Isla Fisher

Isla Fisher

The 'Bad Romance' hitmaker once mistook the 'Confessions of a Shopaholic' star for the 43-year-old 'Enchanted' actress when they met at a star-studded Hollywood bash, which saw the 31-year-old singer praised Isla for her role in 'American Hustle'.

Speaking about the awkward moment on 'Jimmy Kimmel Live!', the 41-year-old actress said: "I remember one time I was at this fancy Hollywood party, the Vanity Fair [Oscars Party]. And I was there, excited, all dressed up, at the bar and schmoozing with showbiz types. And the crowds parted and there was Lady Gaga and she's heading right towards me. And she says, 'Thank you, your performance in American Hustle, Amy, was amazing.'"

But Isla - who has Olive, nine, Elula, seven, and two-year-old son Montgomery with her husband Sacha Baron Cohen - has admitted she "loves" the musician "so much" that she didn't correct her on her mistake.

Isla said: "And I'm thinking, 'Oh my gosh, it's Lady Gaga I love her so much I don't want to tell her the truth.'"

But Isla soon regretted accepting the kind words from Lady Gaga - whose real name is Stefani Germanotta - because Amy was also at the event and was walking near to the pair during their conversation.

And in an attempt to avoid any embarrassment the 'Keeping Up With the Joneses' funny woman decided to point out Amy to the blonde beauty, but pretended the star passing them by was Isla instead.

Isla explained: "I look over her shoulder and there's Amy Adams walking into the party. So, I'm like, 'There's Isla Fisher'."

Although Amy and Isla share some similarities, Isla has decided to point out the differences between the two red heads to avoid any further confusion.

She said: "I am not Amy Adams. Amy Adams and I are completely different people. Let me explain. Amy Adams has auburn red hair, my hair is light auburn red. Amy Adams played Susan in 'Nocturnal Animals'. I played Laura in 'Nocturnal Animals'. Amy Adams has five Oscar nominations. I am a member of SAG."