Exactly what it says it is.

"A dramatic interpretation of Sir Mix-A-Lot's 'Baby Got Back' as if it were performed by actor Sir Ian McKellen."

Via Throwing Things.

Sir Ian McKellan explains what acting is.

A brilliant bit from the Ricky Gervais sitcom — not to be confused with a "shitcom" — "Extras," the first 2 seasons of which we've been watching/rewatching on HBO Video on Demand.

ADDED: The source for that coinage:

Darren: It’s shit. It’s a shit sitcom.

Andy: It’s a shitcom.