
And the answer was ELEPHANT.
The Big Bang Theory Season 4, Episode 24

If I had an ELEPHANT
named Topsy,
The Big Bang Theory Season 11, Episode 8

And I will return to New Delhi in triumph
atop a bejeweled white ELEPHANT.
The Big Bang Theory Season 6, Episode 20

As a bit of an ELEPHANT seal buff...
The Big Bang Theory Season 8, Episode 23