Panic

Pikmin in Pikmin 2 scurrying off in a panic due to the smell of Mitites.

Panic in the Pikmin series refers to any non-lethal event that causes Pikmin to scatter and thrash around in random directions. In a panic scenario, something has scared or affected them to the point where they separate from a leader and run off, and while these Pikmin are not in any direct danger, they risk running into a more dangerous hazard or an enemy. A panicking Pikmin can be returned to normal by whistling it. In Pikmin 2, Purple Pikmin are immune to some types of panic. In Pikmin 4, Oatchi is not (and cannot become) immune to panic, unlike with most other hazards.

Sources

In Pikmin 2, Pikmin in a panic will behave differently depending on the exact source of panic. In Pikmin 3, panic scenarios visually affect Pikmin, and though they spread out in random directions, they will eventually stop panicking on their own accord.

There are several scenarios that prompt Pikmin and Oatchi to panic:

Mitite – an enemy that will cause temporarily panic. In Pikmin 2, Purple Pikmin are immune, and if the Pikmin start the panic whilst in a leader's group, they will eventually return to formation on their own accord. If not, they will stand in place and idle once they are done panicking. The smell of Mitites is what causes this effect.
Emperor Bulblax – a boss whose roar will cause Pikmin to panic. All the rules of the Mitite-induced panic apply to this scenario.
Sovereign Bulblax – a boss whose roar will cause Pikmin to panic, like the Emperor Bulblax.
Antenna Beetle – an enemy that makes Pikmin under its control panic when it's killed. Pikmin will not exit this state unless whistled.
Bulbmin – an enemy that makes child Bulbmin panic when killed. Like with the Antenna Beetle, they will not calm down until they are whistled.
Vehemoth Phosbat – a boss that can spray a cloud of dust that causes Pikmin to panic, clouded in dust. Although some speculate that this is poison, the two have different effects, and, internally, White Pikmin are not immune to this dust.^[1]
Toady Bloyster – an enemy that, in Pikmin 3 and Pikmin 4, can spray ink when Pikmin are attacking, cloaking the affected Pikmin in ink and causing them to panic.
Sputtlefish – an enemy that also coats Pikmin in ink, resulting in the same effect.
Smoky Progg – The Smoky Progg's roar is especially dangerous, as panicking Pikmin may run directly into its gloom and die.
Ancient Sirehound – The Ancient Sirehound gains a panic-inducing roar in its final phase, and like the Smoky Progg it can cause mass casualties if it makes Pikmin panic into a patch of gloom.
In Dandori Battles, an item allows players to splash their opponent with ink, scattering the opponent's Pikmin and respective dog.

Gallery

An Emperor Bulblax roaring.
Young Bulbmin scattering around.
A Pikmin under the effect of an ink cloud. Notice its bigger eyes.
Two White Pikmin inked by a Sputtlefish. This shows how they are not immune.
A Yellow Pikmin under the effect of the purple dust released by the Vehemoth Phosbat.