Who played Sheldon Cooper in 'The Big Bang Theory'?

What is the name of the time machine in 'Doctor Who'? Which streaming service launched 'The Mandalorian' in 2019? In 'The Big Bang Theory', in which city do the characters live? In 'The Big Bang Theory', which character says "Bazinga!"? Which 'The Big Bang Theory' spin-off follows Sheldon's childhood in Texas? In 'How I Met Your Mother', who is the narrator telling the story to his kids? In 'How I Met Your Mother', which character's catchphrase is "Legendary"? Who played Barney Stinson in 'How I Met Your Mother'?