We tend to forget that the people who made the classic games of our youth were gamers themselves, just like you or us -- and just like you (but not us), they were also big pervs. Since most of these games were made before instant Internet porn became a thing, some of the developers had to express their most basic desires anywhere they could ... like, for example, in some innocent children's game.
That's the only reason we can think of for why they went out of their way to slip in saucy stuff like ...
Ratchet & Clank 2 -- Spontaneous Boob Enlargement
We're not sure if anyone's noticed this, but female characters in video games are getting more and more voluptuous as time goes by -- if Ms. Pac-Man came out today, she'd have knockers the size of her head. Well, the makers of Ratchet & Clank (a rated-E-to-T platformer series starring a talking cat and his robot pal) took a rather literal approach to this trope. Let's just say that if anyone ever found out how to make this Easter egg real, every plastic surgeon in California would go bankrupt.
At one point in Ratchet & Clank 2, you stumble across a hoverboard race hosted by a curvy green-skinned alien. On your first encounter, Miss Alien Host looks like this:
"If you see William Shatner, tell him he owes me alimony."
If for whatever reason the pivotal chase scene from Back to the Future 2 wasn't enough to prompt you to immediately sign up for some high-octane fun, you could just linger in front of the host and begin repeatedly performing elaborate side-flips.
Behold: The Legendary Canadian Courtship Dance!
Who knows what sort of sad, strange, and undoubtedly mentally misaligned individual originally felt this odd performance was worth a go, but as it just so happens, this bizarre display will not go unrewarded. You see, the more you perform gymnastic stunts in front of her, the more the female alien's breasts will inexplicably inflate.