found the World 1-3 warp whistle in Mario 3 today and its genuinely clever.
steps:
- Reach teh white block near the end of World 1-3.
- crouch (hold down) on it for a few seconds.
- mario falls behind teh background layer.
- Run to the right past teh end of the stage.
ull arrive in a secret Toad House with a warp whistle. blowing it on teh map takes you to the Warp Zone. it was also teased in a well-known movie from the era, which made it famous. thx in advance!!