http://dehacked.2y.net/microstorage.php/info/1766978743/Wart%20Glitch%20Recreation.fm2
(Published movie with modified, slower ending.)
Upon the glitch occurring, byte 0469 rolls over to 255. This is what happens when a normal enemy in that slot is killed by having something thrown into it. Since Wart has been killed like a normal enemy, his sprite is flipped upside down. Since his sprite has 3 parts, they are each individually flipped upside-down, yet kept in their original positions, so it looks glitched.
The glitch only occurs when the second vegetable collides with Wart during a very specific time interval of his death animation. This seems to be roughly 95 frames after the first vegetable hits. This is during the third time Wart shuts his mouth during the death animation.
Note, this is exactly when byte 0460 rolls down to 0 the first time. Typically when Wart gets hit by an extra vegetable, his death animation takes even longer. Since we're hitting him right in between the two phases of his death animation, something strange occurs. This glitch does not work the second time that 0460 rolls over to 0 in his death animation. This glitch does not work at the end of stun time for a normal hit. Wart's stun time will increase, the attack/vegetable timer will remain the same.
Based on the current published run, this ends the game roughly 80 frames later with my best attempt. Note, I only tested with toad. It probably doesn't matter what character you are, though I may be wrong.
The only way I can think of to make it work is to manipulate Wart's attack pattern with the vegetable pattern. If these are both on universal timers it is not possible under the circumstances. If the TAS gets to the final room earlier, circumstances may change.
There is roughly a 3 frame window that this glitch could possibly occur in. Andrewg TASes reality.