We present longslit optical spectroscopy of three high surface brightness Magellanic irregular galaxies . This paper draws attention to our detection of He I \lambda 5876 line emission from the ionized gas outside the HII regions , or the warm ionized phase of the interstellar medium . We measure a mean reddening-corrected intensity ratio of He I \lambda 5876 / H \alpha \approx 0.041 independent of spatial location . This ratio is much higher than that measured in the diffuse , warm ionized interstellar medium of the Milky Way ( Reynolds & Tufte 1995 ) . The high value of He I \lambda 5876 / H \alpha implies the helium ionization fraction is approximately equal to the hydrogen ionization fraction in the diffuse ionized gas ( DIG ) . If the DIG is powered by young stars , then stars hotter than 40,000 K must contribute to the Lyman continuum radiation reaching the DIG . Since optical and ultraviolet spectra confirm the presence of such massive stars in these galaxies , stellar photoionization remains the most likely power source . The contrast with the low helium ionization in the Galactic DIG , however , is intriguing and provides strong evidence that the physical state of the DIG , not just its presence , varies among galaxies .