Former Idol winner Carrie Underwood returned to the show to belt out Before He Cheats with Alaina, while McCreery paired with Tim McGraw for Live Like You Were Dying.
Funnyman Jack Black teamed up with finalist Casey Abrams for the Queen classic Fat Bottomed Girls, while fan favourite Haley Reinhart landed a duet with Tony Bennett on Steppin' Out With My Baby.
The female contestants also paid tribute to Beyonce with a medley of her hits before they were joined by the R&B diva herself, who sang a verse of Crazy In Love. Beyonce reappeared later to debut her new single, 1+1.
Lady Gaga also put in a memorable performance as she sang Edge of Glory at the top of a fake volcano - before plunging into it.
The TV spectacular also featured performances from judges Steven Tyler, who left his place on the panel to perform the Aerosmith hit Dream On, and Jennifer Lopez, who appeared with her husband, Latin singer Marc Anthony.
Bono and The Edge introduced Broadway show Spider-Man: Turn off the Dark to Idol audiences as the show's star Reeve Carney joined the U2 rockers for a rendition of Rise Above 1 from the musical.
And one of the evening's biggest surprises was a reunion of TLC stars Tionne 'T-Boz' Watkins and Rozonda 'Chilli' Thomas, who recruited rapper Lil Jon and finalists for performances of their hits Scrubs and Waterfalls.
The 10th series of the hit TV talent search has featured visits from a number of guest mentors, including Babyface, Sheryl Crow, Gaga and Beyonce.