The Bridesmaids star announced her engagement to comedy writer Michael Koman in December (11), and the pair is busy planning its nuptials.
Kemper spoke about her relationship during a recent recording of DeGeneres' talk show, but the chat was cut short when an alarm rang out through the studio.
DeGeneres feigned surprise as a male in a fireman's uniform entered the set - but her prank was soon revealed when she handed Kemper dollar bills to use with the stripper.
Kemper screamed in mock horror and exclaimed, "Oh my God" when 'Clayton' ripped off his jacket as LMFAO's Sexy and I Know It started playing, and she began giggling hysterically as the hunk stroked her arms.
The bride-to-be appeared to enjoy herself as Clayton tore off his white vest and danced provocatively in front of her, before lying across her at the end of his routine.
Kemper seemed breathless as she said, "Thank you, thank you so much" and threw the dollar bills over the stripper as she declared, "Take it all!"
The full interview airs in America on Monday (28May12).