The singer was top of the bill at BBC Radio 2 Live In Hyde Park on Sunday, where she performed their 1989 duet Especially For You.
Midway through the song, she said "I need a dance partner" and Donovan came out on stage to pick her up and spin her around.
Minogue opened her set in a fuschia fringed poncho to perform the title track from her new album Golden, before asking the crowd: "Is it too soon to go the disco?" and pulling off the poncho to reveal a fuchsia dress covered in pink rhinestones and transitioning into Spinning Around.
During a brief technical difficulty, when she told the crowd she had been asked to fill time, she sang the introductions to some of her older hits, including Step Back In Time, joking: "I know I've got enough hits to keep filling."
After versions of It's In Your Eyes and Can't Get You Outta My Head, she changed into a floral sequinned dress and was joined by a gospel choir for Especially For You.
After Donovan twirled her around on stage and the pair embraced, she told the audience: "Where do we go from there? I had no idea that was going to happen!
"Thank you Jason. We travelled back on time there."
Continuing with her back catalogue, she also delighted fans with renditions of Locomotion and I Should Be So Lucky before she was joined by Rick Astley to sing his hit Never Gonna Give You Up and Kids, the duet she originally released with Robbie Williams.
Minogue, who celebrated her 50th birthday in May, said both Donovan and Astley had been at her party to mark the occasion, adding: "50 happened this year and for more than half of those years I've been with quite a lot of you."
She went on to thank her fans for sticking with her through "the ups, the downs, the middle of the road, the got it right, got it wrong".
Minogue closed her show with renditions of Love At First Sight and All The Lovers.
Other acts to perform at Radio 2's one-day festival included Lenny Kravitz, Boyzone and Manic Street Preachers.