Jono and Sharyn picked a random contact from Ben's phone and told him he needed to ring the person they've picked out for him.
Too bad Jono and Sharyn saw that Ben's got Clarke Gayford's number saved in his phone so they dared Ben to ring him and say the L-word to see if he says it back.
First call was a failed mission. Clarke just said:
Good thing Jono insisted they ring Clarke again and have another go. And then he finally did say it back to Ben:
Hahaha. I love you to.