♪ The Earth BEGAN to cool ♪
The Big Bang Theory Season 5, Episode 20
Now, I'm sure many of you are wondering
how Fun with Flags BEGAN.
The Big Bang Theory Season 10, Episode 21
♪ The Earth BEGAN to cool
The Big Bang Theory Season 12, Episode 23
♪ The autotrophs BEGAN to drool,
Neanderthals developed tools ♪
The Big Bang Theory Season 5, Episode 17