Mr. Beckett was pouting as they left the dental office while Jenny was gloating. She'd already messaged Kim that she had won Christmas eve without any context, and Kim had responded with two thumbs up. Andrew was tired, his gums hurt, and he just wanted to get back home.
Andrew was having a hard time wrapping his head around these two people in his life behaving this way. Andrew had viewed Mr. Beckett as a bit more of a stoic man. More subtle, but he wasn't behaving that way at all.
Jenny? He hadn't had enough interactions with her yet to get a read for her personality. She did remind him of his Mom though. The way she was able to guilt trip him without doing much was very reminiscent of his Mom. It was a good and a bad memory.