Fergie went stage crashing on Sunday night... not once, but twice.

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The singer attended The Trevor Project's TrevorLIVE L.A. Gala on Dec. 3, which honored Tom Ford this year. As Armie Hammer stood on stage presenting Tom with the Hero Award, Fergie walked onstage unexpectedly. Some people thought she was part of the schtick, but soon discovered it was all unplanned.

"Oh, yes!" a surprised Armie said, according to E! News. "Ladies and gentleman, Fergie!"

The Fergalicious one said, "No, I'm not Fergie; I am actually Armie Hammer. Thank you. I am going to win at the Academy Awards. Thanks! So, this is unexpected, and in typical Tom Ford style, I think he would love that—if he was here."

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Tom was there, though, and his presence wasn't exactly a secret, given that he sat at the head table.

"They really love you. They do! They really love you!," Fergie bizarrely continued. "But, uh, Tom Ford is here. He's here on this bag. He's here on this amazing T-shirt, mock-style, long-sleeve shirt and fabulous skirt and pumps. But, he's also here as a person. And the thing is, behind all the Tom Ford life, which I thrive to get—I was really embarrassed that I didn't have Tom Ford makeup in my bag, by the way; so shaming—he is a person of compassion. He's a director. He loves to see people's feelings and listen."

She then started plugging her new album (which is available at Target, she said). After that, she started singing verses from her song "A Little Work."

As the crowd watching in confused amusement, she then said, "I'm still Armie Hammer, and this is the first time I've ever sang for you guys in my life. And now I'm going for my Tony! Thank you so much!" Still pretending to be Armie, she then said, "Welcome, everybody, Fergie!"

As she exited the stage (one that she was never invited onto) Armie tried to make light of the stage crashing. "If I had a nickel for every time that I was confused with Fergie," he joked.

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Later in the evening, Shoshana Bean was set to perform, but there were sound issues, so she walked off the stage while the glitches were worked out. Again, in stepped Fergie, who attempted to suddenly lead the crowd in a singalong of her son, "A Little Work," which few people, if anyone, knew the words to.

"Just, I guess, with full shame or no shame, I don't know, get it on iTones…iTones? That's a new one. iTunes," Fergie continued. "Anyway, just get it if you want. You know what? Listen if you want. If you like it, listen, if you don't—don't! But it's a song that is really personal to me and...Give it up for Tom Ford! Trevor Project! This project. I wasn't even planned to speak tonight, but I guess I can't stand it when everyone else is up here singing. Um, but this project really means so much to me. I mean, honestly, reading about the suicide, uh, percentage and—"

Fergie was then interrupted by an overheard voice reintroducing Shoshana.

Gala attendees Elizabeth Chambers and Isla Fisher "were loving it," a guest told E!.

"They were laughing and taking video. Their eyes were also wide, clearly shocked, and based on their reactions it made Fergie's stage appearances seem that much more of an impulse on her part," the guest said. "Everyone was genuinely surprised by how Fergie was acting."