thats exactly what this OVA is.
it consists of two plots, the first half is Zapp fending off hoards of monsters because of a dispute with his love interest. The second half involves an extreme drinking contest between a monster and Chain.
because its an OVA, nothing is really supposed to be taken seriously so the plot is very linear/predictable with little depth to them. its just supposed to be an opportunity for the audience to see their favorite characters be "wacky" and "zany" without messing with the main plotline. while that might not be everyone's cup of tea, its not necessarily a bad thing if its done well, and i think it was done will. it was funny (more like goofy with the overexaggerated facial expressions etc.) and it was light hearted. the quality of the OVA is solid too so its not like there was no thought put into it.
id say its a good change of pace if youre trying to break up any longterm animes youre watching.
