I remember I used to lurk on IGN Nintendo boards right around the time the Wii came out and a little bit before the launch. There was a subgroup of posters that were convinced that there was some hidden secret extra horsepower hidden underneath the little flap in the front and Nintendo, like a trap card that Nintendo was going to reveal any moment. All that hype was predicated on one single throwaway line by Iwata when he said "the Wii will make you say 'wow.'"
I don't remember the flap + secret horsepower* stuff, but I
do remember there being a 6-month period in the Nintenblogosphere (please god never let me type that again) where there was rampant speculation about what WAS under the flap. The theory that convinced the most was that it was either a projector (

) or some kind of expansion slot like the N64 (with the 64DD) and GameCube (with the GameBoy Player) had.
You have to remember, this was barely weeks after the entire Nintendo fanbase (myself included) got duped by Nintendo ON.
This is still the most popular video I ever uploaded. Across both my YouTube accounts.

* I do remember there being a lot of talk about how devs weren't properly getting all the horsepower from the system because they were using shitty unoptimized cross-platform engines and/or were also "super lazy." Which I mean, you look at Galaxy and then you look at an average third-party game and that's pretty easy to buy (but it ignores sooooo many other factors, obviously.) I also remember talk of the system being able to output 720p somehow since "some games on the PS2 did it" and "component cables sorta support 720i which I guess is close enough?" I don't think there were ever any Wii games above 480p though.