Blooper

The end of the movie apparently takes place when the softball team has a spring practice. However, we see that the leaves are changing.

When Danny enters the bar on St. Patrick's Day he is soaking wet. When he and Debbie go outside seconds later Danny is completely dry.

When Danny and Bernie are on the roof, Danny's collar is alternately flipped up/down between shots.

At the beginning of the movie Debbie and Joan are newcomers to Mother Malone's but on St Patrick's Day Debbie demands that Danny stop stalking her at her hangouts. This was clearly his place.

The softball that Bernie is holding goes from a Chicago-style 16 inch clincher softball to a 12 inch ball and then back to a 16 inch ball again.

During the breakup scene Debbie turns on the light next to Danny and makes the comment about not being in the dark anymore but when the scene ends and it cuts back to Danny the room is dark again.

When Danny chases Debbie out of "Mothers" and into the rain on Division Street, you can see, far in the background, the sign for the real Mothers which is actually a block away. The bar used as the exterior of Mothers was actually the Alumni Club.