why did eddie get mad?

He was mad because, if you remember, the day before when they were talking she said about herself "what you see is what you get" and that, in fact, was not entirely true. He didn't appreciate being lied to/not being told the truth, which he says after the show. I hope that helps you!

Maybe his getting mad also is supposed to show that he really cares about her, because ordinarily it would seem he would take such a thing in stride. I felt it was out of character, too, though, and was wondering about this as well. It was the one red herring in a show that otherwise hung together quite well ... along with the awkward, my-face-is-red kiss at the end. I also did feel the whole bull-cow thing was cute but somehow didn't really go with the story, maybe because the environments were so different. That's not really an indictment ... a little Green Acres perhaps. After all, there's dairyland maybe not even 20 or 30 miles from Manhattan. But why would there have been a big picture window photo of cows behind Jane and Eddie as we zoomed out during the kiss? The original name of the movie appears by the publicity still to have been Animal Attraction. That might have tied things better for me. Maybe there could have been an even better title to have tied everything up neatly, like something to do with instincts. If I think of something, I'll add it here. Anyway, yes, Eddie's having gotten mad and run did seem to not fit with his generally laid-back schtick, although of course we discover that he felt a lot more deeply than we knee-jerk ascribe to a womanizer.