Nobody wants to see their parents in a sexual context, much less in one in which your dad is pretending to be a feeble woman and your mom is pretending not to have just busted in
his her pants. But to watch some other kid suffer through it is hilarious.
I could go into the clever framing devices employed here, or the interwoven narrative arcs expertly playing with diegetics, mimetics and the assumptions of the viewer to create the multiple instances of connotative humor and suspense, all of which result in this advert being almost worthy of the title of literature, but then I'd sound as geekily nerded-out as I am, so I won't bore you with the details.
What's important is the heartwarming fact that these (misguided?) parents thought this was a great gift for their son (they must have rehearsed for hours), and also the fact that they each acted out the scene with a thespian's enthusiasm and integrity to their chosen characters, after switching genders, making this advert one of the best we've ever seen.