The reality stars cuddled up to Jason backstage, where they were all set to appear on Celebrity Big Brother's Bit On The Side: Rylan's Supersized Celebrity Sunday.
Jason appeared on the show to sing his new song, 'Talk Dirty', while Lucy and Ollie were guests. Posting a photo of the pair to Instagram, Lucy said: "Ummmm @jasonderulo is the coolest."
But Lucy probably wasn't expecting Jason to return the favour. The 23-year-old 'In my Head' singer, who wore a khaki vest top and thick gold chain, said: "I don't know, you were pretty damn cool yourself! Nice to have met you."
Lucy came dressed to impress for her TV appearance, and once again showed her love for a good high street bargain.
Keeping it simple yet chic, Lucy wowed in a white floral print playsuit from Boohoo.com, pointed orange heels from Office and a gold belt clutched at the waist from Missguided.
Meanwhile, Ollie, who will not be returning to the E4 reality show, also gave Jason plenty of compliments.
He said: "Ok.. So casually just spent the last 2 hours with @jasonderulo lovely, hilarious and absolute legend!!"
Jason, who is dating US singing sensation and former American Idol winner Jordin Sparks, replied: "@ollielocke fun my dude! #goodlaugh."
Watch Jason Derulo performing on BBBOTS below: