The Room/Fridge

Possibly unintentional, but Hit is another word for wanting to have sex with someone, so in a sense, Lisa WAS telling the truth when she said Johnny "hit" her.
- Definitely unintentional, otherwise we're crediting Lisa more intelligence than she has.
Mark tries to pressure Johnny into telling him confidential information from his work. Johnny then follows up by asking: "How's your sex life?" Though it seems like a non sequitur, Johnny is trying to show Mark how he is making him feel in requesting personal 'confidential' information.
- Wow, that would be pure genius if anything else in that movie indicated that Johnny was capable of that level of subtlety.
- I occasionally wondered, in lieu of Johnny's "Maybe I know more than you think I do" line later on in the film, if this wasn't perhaps supposed to be a ham-handed hint that Johnny suspects Mark's banging his fiancee. But, of course, that would be implying that Tommy Wiseau is capable of subtlety.

It was said Lisa has been with Johnny for seven years. The actress was 18 and didn't look too much older.
- She is portrayed as being older than the college aged Denny.
Mark's I Have This Friend conversation with Johnny about wondering if girls sleep around takes in a whole new horrific meaning when he talks about a girl cheating then getting the crap beaten out of her. Taken in the context of the nature of the chat, it implies Mark was the one who sent a girl to the hospital. His murderous rage at Lisa at the end of the film does not bode well for her.

If Denny comes over to Johnny's apartment all the time, why has Lisa's mom never met him before the events of the movie?
- I was going to say that maybe that was Denny's first scene in an earlier cut of the film, but then I remembered how seldom characters get introductions in this movie.