Types of humor suitable for RPG level design:
The goal is to masquerade the RPG as "Serious game for serious players", not blatant in-your-face humor: so these ideas should
be used sparingly or limited to level desired from the setting.
These ideas are not fit for epic fantasy game, but for generic RPG setting to spice it up - aiming for both "grand RPG" and "funny RPG" will not work.

1.Naming levels/area with mundane characteristics unfit for "epic fantasy": Seventh Layer of Accounting Department.

2.Monsters with mundane nature mixed with fantasy characteristics or adjective contrary to their nature:Zombie Chihuahua, Demonic Bunny of Doom, Aggressive Potted Plant.
Normal Monsters having dialogue or just ironic quips about their nature(satirizing the "boss battle dialogue" as if every monster is a game-end boss).
2.A.Humor must be generic not referencing material that copyrighted/trademarked or believed to be belonging to a group/subculture:
Avoid pop culture references and copyrighted franchises.
Avoid rare in-joke only accessible only to specific groups/subcultures(other games of genre included).
Avoid memes: they don't age well and alienate players not familiar with or too familiar with the concept.

3.Items with misleading/humorous names: Tactical Apocalyptic Pin(a lance).
Attributes that depend on improbable or unrelated stats(such as current speed).

4.Quests utilizing satire and sarcasm: common targets are RPG tropes( see ) and assumptions of players about the game setting (e.g. "Generic Mideval European Fantasy Setting").

5.NPCs which "don't follow a script" or exhibit unusual/ironic/humorous behavior: arguing with players, joking about the game setting, breaking the fourth wall, running away or hiding from players, etc.