Because the firearm enhancement under Penal Code section 12022.53, subdivision (e)(1) (principal armed in gang enhancement case) has a specific pleading and proof requirement, when the prosecution has failed to comply with the pleading requirement, it cannot be substituted on appeal in place of another gun-use enhancement. Appellants, identical twins, were convicted of attempted murder trial for the benefit of a gang, and the jury found true firearm allegations under Penal Code sections 12022.5 and 12022.53, subdivisions (b), (c), and (d) as to both of them. They argued on appeal that insufficient evidence supported the gun-use enhancements because the victim could not establish which one of them personally discharged the weapon. Respondent agreed the evidence did not support the enhancements as charged, but argued a gun-use enhancement under section 12022.53, subdivision (e)(1) could be imposed instead. The appellate court found the reasoning in People v. Mancebo (2002) 27 Cal.4th 735, and People v. Arias (2010) 182 Cal.App.4th 1009, prohibit the substitution of the enhancement. Like the One Strike multiple-victim circumstance in Mancebo, and the attempted murder statute in Arias, subdivision (e)(1) has an express pleading and proof requirement. Imposition of the enhancement would violate not only the language of the statute but also appellants’ due process right to notice. And harmless error analysis does not apply to the failure to satisfy the pleading requirement. Therefore, the enhancements were stricken.