We report the observation of satellite structures associated with the core C 1s and F 1s levels in the photoelectron spectra of CH3F, CF3H, and CF4. These structures are attributed to monopole "shakeup" excitations. Qualitative assignments aided by theoretical Xα-SW calculations are presented. We found shakeup intensities in the C 1s spectrum of CF4 are enhanced by barrier created by the fluorine lone pair electrons. However, this effect is less apparent in the F 1s core hole photoelectron spectra.