The 34-year-old professional wrestler teamed up with the chat show host to put on the unexpected dance for him after he admitted he couldn't afford to go to the semi-formal event during his school years.
He said: ''I did not [go to prom]. I went to boarding school, and it was a co-ed boarding school so I kinda saw these people all year anyway.
''I was dead broke and I had the chance to stay on campus and earn some money so I didn't go to prom.''
Ellen then revealed Nikki was going to be his date for a surprise prom and the raven-haired beauty revealed herself in a beautiful purple dress.
Upon seeing Nikki, he said: ''I hate surprises but this one I love.''
Ellen then gave John a crown to wear to make him Prom King, and the couple enjoyed an awkward slow dance to Lionel Richie hit 'Three Times a Lady'.
Nikki joked: ''We can't dance like this on our wedding.''
Earlier in the episode, 40-year-old John admitted he felt really anxious about popping the question to his bride-to-be on WrestleMania 33 last year.
He said: ''I was super nervous, but I was definitely ready to ask her and that's a big change of opinion for me. It took me a long time to get to that point, five years.''
Nikki - who started dating John in 2012 - admitted afterwards she had an inkling the pro wrestler was going to propose.
Speaking last year, she said: ''You know what, there was a lot of speculation but his mom was sitting front row - first time she's ever been to a live wrestling event in over 16 years.
''I was like, maybe this is for me, oh no, there might be a swerve to his mom, and then it was for me.
''And then I forgot how to breathe and I got really nervous and I said 'yes.' ''
Once a fire fighter, always a fire fighter.
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