♪ The Earth BEGAN to cool ♪
The Big Bang Theory Season 5, Episode 1
♪ The autotrophs BEGAN to drool,
Neanderthals developed tools ♪
The Big Bang Theory Season 5, Episode 2
♪ The Earth BEGAN to cool ♪
The Big Bang Theory Season 5, Episode 10
♪ The Earth BEGAN to cool
The Big Bang Theory Season 7, Episode 23
♪ The Earth BEGAN to cool ♪
The Big Bang Theory Season 12, Episode 15