It's Darth Vader SHAMPOO.
The Big Bang Theory Season 1, Episode 1
And also, while we're on the subject,
you recently changed your SHAMPOO.
The Big Bang Theory Season 6, Episode 2
You've convinced me, maybe we should
sneak in and SHAMPOO her carpet.
The Big Bang Theory Season 1, Episode 2
Only to SHAMPOO
Professor Shamburg's shih tzu.
The Big Bang Theory Season 3, Episode 14
...and my new dandruff SHAMPOO
doesn't smell like tar.
The Big Bang Theory Season 6, Episode 6