It means your character doesn't have sprites for the ^ frame. (ignore the "A1" after "TAIL" that's a bug I think)
If you're using SLADE, enable the "Use percent encoding if needed outside of Wad Archives" option in the Preferences window (in the Editing tab). It's likely that SLADE decided to remove ^ from the sprites that should use it.
The other possibility is that new mass-renaming feature of SLADE messed you up (if you used it), apparently ^ is reserved for some formatting thing now.