Brief of The Big Bang Theory

Season 1: Penny showed up.

September 24, 2007 - May 19, 2008

Penny * (portrayed by Kaley Cuoco) removed to the building and became part of the unearthly scientific group. Having broken up with couple of ex-boyfriends, she accepted Leonard's date.
Leonard Hofstadter (portrayed by Johnny Galecki) is always being made fun of on his small achievement in science. But he is the core of the group and finally hit on Penny.
Sheldon Cooper (portrayed by Jim Parsons) is a lucky man who lives in his own cosmos. But everbody loves him.
Howard Wolowitz (portrayed by Simon Helberg) is a teeny-tiny man living with his mother who always trys to show off himself to every girl he comes across.
Rajesh Koothrappali (portrayed by Kunal Nayyar), instead, can't speak any word everytime he comes across a girl. But he starts to change this awkward situation a little bit, like taking pills.
Sara Gilbert as Leslie Winkle is a absolutely rational scientist and the only one who made fun of Sheldon without a counterattack.

September 22, 2008 - May 11, 2009

Penny worked in a restaurant of Cheesecake Factory. And the very one deep in her heart turned out to be Leonard.
Leonard struggled all his life.
Sheldon started three-times-knock when he paid a visit to others.
Howard sended a toilet to the space.
Rajesh looked at the stars.
Kevin Sussman as Stuart Bloom and his comic book store showed up.

September 21, 2009 - May 24, 2010

Melissa Rauch as Bernadette Rostenkowski showed up and became Howard's girlfriend.
Mayim Bialik as Amy Farrah Fowler was matched by an online dating site as Sheldon's perferct mate at the end of the season.
Penny and Leonard kept a relationship and had some fun but broke up at the end of the season.

September 23, 2010 - May 19, 2011

Amy claimed herself as Penny's best friend. With Bernadette they hanged out together in girls' night.
Aarti Mann as Priya Koothrappali form India became Leonard's girlfriend.
Howard got engaged with Bernadette.
Sheldon often had video chat with Amy, which comforted him a lot.

September 22, 2011 - May 10, 2012

After preparing for their wedding for the whole season, Howard and Bernadette finally celebrated it.
Penny and Leonard started beta-test for their relationship before release with bug report when they went into conflict.
Shldon and Amy moved their relationship to the next level -- had a contract to formulate the rights and obligations as girlfriend and boyfriend.
Raj? The best man of Howard.

September 27, 2012 - May 16, 2013

Raj finally had a long relationsip, for a season, with a girl Kate Micucci as Lucy but ended up with too much push. But this tragedy resulted in Raj could talk to women without alcohol as his heart was open.
After 3 years, Sheldon and Amy had a intimate intercourse, fictitiously.
Leonard and Penny maintained a relationship for the whole season.
Howard? Became the master of Dungeons & Dragons.

September 26, 2013 - May 15, 2014

Raj had a "girlfriend" Laura Spencer as Emily.
Penny moved on to her acting career but finally quited and had engaged with Leonard, seriously.
Sheldon lived a life but his career went into a turning point.
The Wolowitzs just went on but Stuart lived with their Mom.

September 22, 2014 - May 7, 2015

Howard's mother, Mrs. Debbie Malvina Wolowitz (voiced by Carol Ann Susi), had passed away.
Raj's parent, V.M. Koothrappali (Brian George) and Mrs. Koothrappali (Alice Amter), got divorce.
Sheldon's and Leonard's mother, Mary Cooper (Laurie Metcalf) and Beverly Hofstadter (Christine Baranski), met each other.
Amy was mad at Sheldon's inconsideration.
Penny and Leonard went to Las Vegas for wedding.

September 21, 2015 - May 12, 2016

September 19, 2016 - May 11, 2017

Penny had another wedding ceremony with Leonard as both family and friends were around, Bernadette gave birth to a baby, and Raj started paying bills by himself. It is what we called life itself. Sometimes it is just going on.
Sheldon proposed to Amy.