CREDIT IF REPOSTED
At the end of "My Ages Apart", there was a post-credits scene about Lily Li playing with a weighing machine in a movie theatre, which also ended up changing time and space. Then the camera shot changed from Lily to Charmaine Sheh. During the programme after the series finished airing, this series' producer, Joe Chan, revealed that Charmaine guest-starred for free this time.
*Credits to on.cc