'Big Bang Theory': What just happened?

bbt-100th-ep-cbs.jpg Chuck Lorre seems to have a thing with deus ex machina. He used it with "Two and a Half Men" earlier in the season. And as they say, "If it ain't broke, use the same embarrassing plot device again." Lorre did just that on Thursday's (Jan. 19) episode of " The Big Bang Theory."

[Spoiler Alert?]

It seems like just yesterday Leonard ( Johnny Galecki) and Penny ( Kaley Cuoco) first met on the nerd comedy. But in reality, it's been 99 episodes. So for the 100th, producers went back to revisit the on again/off again relationship between the two. Well, sort of.

Leonard insistently asks Penny out on a date. And, whether she knows what she's getting into or not, she agrees. This turns into a pleasant dinner periodically interrupted by Leonard saying ridiculous things like, "So what do you think? Are we going to get back together?" The evening quickly devolves into bickering and, ultimately, make up sex.

This pattern repeats itself over the course of the half hour. Leonard says something dumb. Penny yells at him. He gets irritable. She storms off. Then she texts him in the wee hours of the morning for a late-night booty call.

Ultimately...oh nevermind. The whole thing was a scenario Leonard dreamed up. They never did get back together. The dinner never existed. The bickering didn't. And neither did the make up sex. Nothing happened except Chuck Lorre using the plot device you're taught not to use on the first day of Screenwriting 101.

On a scale of 1-to-Pi, Thursday's episode was Absolute Zero, or in thermodynamics −459.67.  

Photo/Video credit: CBS