Pokémon - What does it even mean to be a half-normal type (that's not a bird)

"Normal" is both the default Pokemon type and one that has its own identity. Most importantly, the Normal type is the versatile type. That's why Normal moves are so common (about 20% of all moves), why so many Normal types have great TM coverage options, and why Pokemon whose gimmick is shifting forms or specialty usually default to Normal (Kecleon, Ditto, Silvaly, Eevee, etc). This is also reflected in Hidden Power, a Normal move that becomes other types, and the card game, where Normal types are colorless and can use any type of energy.

Normal also has a couple of sub-specialties, like several other types. For example, the bulk of sound-based moves are Normal type (Growl, Hyper Voice, Roar, Screech, Uproar, etc). Therefore, many Pokemon that have an emphasis on sound are Normal type (Whismur, Jigglypuff, Chatot, Meloetta, etc). Even Pyroar may be an example, since it learns moves like Noble Roar, Echoed Voice, Roar, and Hyper Voice.

Bibarel is a dumb but really erratic, wet beaver.