
♪ The Earth BEGAN to cool
The Big Bang Theory Season 5, Episode 15

♪ The Earth BEGAN to cool
The Big Bang Theory Season 7, Episode 20

# The autotrophs BEGAN to drool,
Neanderthals developed tools #
The Big Bang Theory Season 11, Episode 14

Wondering how it all BEGAN?
The Big Bang Theory Season 10, Episode 21

♪ The Earth BEGAN to cool
The Big Bang Theory Season 12, Episode 18