Finch doesn't know who his father is
- Finch's mom doesn't seem to be all that much older than he is, and she liked to cut loose with lacrosse players when she was in high school.
Stifler wasn't talking to Oz for the rest of the first movie after he abandoned the final game
- It's likely that the team would have lost without Oz's contribution, and lacrosse obviously means a lot to Stifler, so he must have been upset with him. Oz, post Character Development, definitely wouldn't have told Stifler that he did it for reasons of being sensitive to his date's emotional needs and because he just wanted to of his own volition. So the two weren't speaking during prom and for a while after. However, as they have been Vitriolic Best Buds for some time, and end up in the same college as shown in the sequel, Stifler eventually got over it later that summer.
Erik's dad is also Steve and Matt's real father
- Steve's dad had a very messy divorce with his mom because of an affair he had with one of his coworkers. The divorce was finalized shortly after Matt was born. After that, Mr. Stifler just wanted to start over and ended up marrying the woman whom he had the affair with and that's how Erik was born. Erik being Steve and Matt's cousin was just a family lie to make everything less awkward between him and Matt.
