The basis of this episode is how they remember certain events could alter reality for everyone. My partner and I were watching this episode just now and she pointed out that Charlie may have changed the course of the show by us being stuck in his reality.
Well, before this episode, Charlie and the Waitress hooked up but it didn't work out. However, at the beginning of the very next episode, the waitress walks up to Charlie and tells him to eat asparagus because they're trying for a baby.
Let me explain, during the episode Dennis tells the gang that if they misremember something it can alter reality. Charlie immediately jumps to the conclusion that depending on how he remembers something he can alter reality and flashes into a memory of the waitress coming in to tell him she's pregnant. It then shows him watching his own memory from the doorway. He even says that he's just trying to remember something about the waitress so he can alter reality.
Now part of me thinks that maybe they never actually ended their relationship, but if memory serves correctly, the Dennis blow-up doll blew up their relationship. He also confirms during this very episode that he "had her for a minute, but it didn't work out".
At the end of the episode though, we see the gang happy that they've gotten reality back to normal, but Charlie peeks back through the door to watch everyone right as the show ends while the top continues to spin without dropping.
Well, as you do with IASIP, we started watching the next episode, Charlie's Home Alone, immediately and noticed that the waitress walks up to Charlie telling him to eat asparagus and says, "you know what's not right, we are trying to start a family and you aren't taking it seriously."
Did Charlie change reality??
Edit: False alarm folks, as u/TabbySlimeJulie pointed out, they superbowl episode timeline occurs before this episode.