When Pam set Michael up on a blind date with her landlady, it ended in a disaster. When Michael ended up dating Pam's mother, it too became a disaster. In Happy Hour, it comes off as ironic, that Pam would dare to set Michael up another time. As predicted, Michael made himself look like a fool, especially with his obnoxious clothing and behaviours. This scene was very reminiscent of the episode of the British series, where David Brent made his dates feel excessively uncomfortable. Where the two men are different, is that Michael is dumb enough that other people are completely unable to realize his level of incompetence, and mistake it for confidence and ability. It's times like this, that Michael is able to turn defeat into victory, as he somehow managed to make a good impression on the bar manager.
While Michael was being overt about his intentions, Andy and Erin were trying to keep theirs secretive. It's a nice homage to when Jim and Pam hid their relationship, but instead of spanning a number of episodes, it only goes for one episode. The scene where Erin sat down in front of that guy, definitely showed a different side to her, that almost contradicts her usual self. It goes to show that Erin is still relatively new to the show, and her character hasn't been fully revealed yet.
As Andy and Erin made their secret public, Dwight tried to hide his contract with Angela from Isabel. However, Isabel was hesitant to believe the idiocy of the contract, and responded in Dwight's favour. Isabel, along with many other guest characters, are just completely unaware that some of the strange people like those that work at Dunder Mifflin could possibly exist, and end up giving them the benefit of the doubt, when it comes to their weirdness and morality.