This week "The Big Bang Theory" wraps up season 9 with a finale episode titled, "The Convergence Convergence." This season has brought the characters closer together than ever before and this episode sets up the path to potentially bring Leonard, played by Johnny Galecki, and Sheldon, played by Jim Parsons, and their parents, into an even closer bond. While it's a very focused plot, basically taking place at only a handful of mostly familiar locations, it's full of nuanced and hilarious moments because of the excellent writing in the script this week.

Leonard's parents and Sheldon's mother cause a stir

We finally meet Leonard's dad, Alfred, portrayed by Judd Hirsh, who recently divorced Beverly, portrayed by Christine Baranski.

These two have an icy relationship since parting ways and are less than thrilled to reunite in Leonard and Sheldon's apartment. Beverly is outraged that Leonard invited him to come, but there's little she can do about it. Meanwhile, Penny questions why Sheldon has invited his mother Mary, portrayed by Laurie Metcalf, to the ceremony and he says he has also tried to invite Stephen Hawking and Robert Downey Jr. to the wedding.

Howard and Raj get an email from the Air Force

Just as the two scientists get proof of concept up and running for their guidance system, Howard gets an email. It's the Air Force and they'd like to set up a meeting to discuss their idea, and it sets in motion some extreme paranoia that the government is watching, listening and following their every move. The paranoia culminates when everyone is on their way to the rehearsal dinner and Howard mistakes Leonard in the car behind him for the government following them.

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He speeds up and tries to shake the car, but ends up pulled over by the police, ranting about how he's not on drugs and how the government is following him.

The season finale cliffhangers

While at dinner, Alfred and Mary get acquainted, much to the surprise of Amy, who figures out quickly that romance is in the air. Sheldon seems pretty oblivious to what is happening, but Leonard is in a state of shock when his dad and Sheldon's mother walk out of the dinner early. Mary and Alfred share a cab and find out they're staying at the same hotel, so they agree to have a drink. The next day Leonard and Sheldon try to contact their parents, who have turned off their phones. Penny, played beautifully by Kaley Cuoco, knows this is a sign that their parents have hooked up and she's laughing and says she loves it as Leonard and Sheldon shake their heads in disbelief and can't believe what's happening. If their parents would decide to get married they'd become step brothers. The season ends on this cliffhanger, so we'll have to tune in next season to find out just exactly what happened the night before and hopefully we'll still get to see Leonard and Penny renew their vows.