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: Focused on major milestones like Howard and Bernadette starting a family and the culmination of Sheldon and Amy’s professional and romantic journeys.

“The Justice League Recombination” (S4E11) – the guys dress as the Justice League for a comic book store costume contest, with Penny as Wonder Woman.

Bob Newhart as Professor Proton, a retired TV scientist who becomes Sheldon’s mentor.

He gives Amy a “relationship agreement” and a tiara from his “emergency gift drawer.” The character is softening without losing his essence.

Sheldon Cooper became an iconic character — infuriating yet lovable — precisely because he changed over 12 years. And the friendship between him, Leonard, Penny, Howard, Raj, Bernadette, and Amy proves that a sitcom built on science and sarcasm can also be about .

She gives birth to a healthy baby boy. Leonard’s dream of fatherhood comes true.

“The Monopolar Expedition” (S2E23) – Leonard and Penny kiss before Leonard leaves for the North Pole, setting up season 3.