Did the Doki Doki Panic prototype use Mario sprites?

Doki Doki Panic initially began as a Mario-style prototype which was vertical instead of horizontal. Unfortunately, they fall short of saying it was a Mario game, only "Mario-style" or "Mario-like." Did they use Mario sprites as placeholders, or did they use something more generic like plain squares/rectangles?

Are there any examples other Nintendo game prototypes using Mario characters as placeholders? If so, it would be fair to assume that the Doki Doki Panic prototype did use Mario.

And if it did use Mario, what do you think the sprite(s) would've looked like? My guess would be the SMB1 sprite, but it would be interesting if the SMB2/SMB3 (they're very similar) sprite was designed prior to the Doki Doki Panic sprites.