♪ The Earth BEGAN to cool
The Big Bang Theory Season 12, Episode 6
♪ The autotrophs BEGAN to drool,
Neanderthals developed tools ♪
The Big Bang Theory Season 5, Episode 12
♪ The Earth BEGAN to cool ♪
The Big Bang Theory Season 5, Episode 1
# The Earth BEGAN to cool #
The Big Bang Theory Season 11, Episode 15
♪ The autotrophs BEGAN to drool,
Neanderthals developed tools ♪
The Big Bang Theory Season 7, Episode 2