Something that cannot be totally explained.

Large, beautiful breasts that are keep well consealed and initially appear to be much smaller and less impressive than they actually are until unleashed.

The frustration after not being able to cum while fapping. (reference to the Christmas PornHub icon of a cute reindeer that stares at you.)

The reindeer effect is as an instance where something that is gross, unattractive, unintelligent, savage, unappealing, or just completely awful in real life is redefined through cartoons and cultural representations as cute, cuddly, cunning, kind, attractive, or appealing. For example, reindeer and most animals or anything else that is personified through cartoons or songs.