he has a thing for Tiffany.（誰か）を気に入っている、夢中,大好き

walk out on　(someone) ： (誰か)の下を去る、見捨てる
What a dog! ： 本当にひどい！
have a thing for (someone) ： （誰か）を気に入っている、大好き

Jan:Hello?

Terry:Hey Jan it’s Terry. You’ll never guess what happened on Days and Dreams.

Jan:Yeah I just saw it. I can’t believe James walked out on Kat!

Terry:What a dog! Do you know why he left? I only saw the second half.

Jan:Well apparently he has a thing for Tiffany.

Terry:But isn’t she supposed to marry Mitch at the beginning of next season?

Jan:Hm… Maybe they’ll have Mitch and James competing for Kat’s love at the start of next season.

Terry:Sounds exciting. I can hardly wait!