What does the progress bar measure?

It tracks the repeated contact with the large furry character; fill it completely to trigger the transformation.

Should I enter one of the visible doors first?

No. Stay with the character until it changes into the tall real Potato form; the victory state follows that transformation.

Mr Potato level guide

hard

Keep contacting the large furry character until the overhead bar fills and it transforms into the tall real Potato form.

Layout: Mr Potato starts on the left side of a flat room. A large furry character stands on the right beneath a horizontal progress bar, with an arched door visible on each side.
Goal: Fill the progress bar through contact and trigger the character's transformation into its tall, legged Potato form.
Opening: Walk right from the left side and approach the large character directly; no key or platform setup is needed.
Danger Zone: The side doors are not the active objective while the progress bar is incomplete; turning away early leaves the transformation unfinished.
Mechanics: Repeated contact advances the overhead bar. When the bar completes, the short furry form grows into the tall version and the level resolves.

Use the white segment of the progress bar as the completion check, not a single collision.
Stay with the large character until the tall form appears, then wait for the victory dialog.
Think in chain clears. The best move is the one that sets up the next two moves, not just the quickest current match.

Start on the left floor and walk right toward the large furry character.
Continue into the character so the overhead progress bar begins to fill.
Keep making rightward contact and use the bar to confirm that the interaction is advancing.
Continue until the bar is full and the character grows into the tall, legged Potato form.
Stop after the transformation and wait for the VICTORY screen instead of leaving through a side door.

Turning back to a side door after the first contact leaves the progress bar only partially filled.
Treating the short furry form as the final state misses the required tall-form transformation.

What does the progress bar measure?
It tracks the repeated contact with the large furry character; fill it completely to trigger the transformation.
Should I enter one of the visible doors first?
No. Stay with the character until it changes into the tall real Potato form; the victory state follows that transformation.