Let's make one thing clear first and foremost; Serious Sam humor has always been groan-worthy dad jokes that are so unfunny that they somehow became funny. So what makes the vast difference in fan reception between them?

After much contemplation, the difference seems to come down to how the authors of these jokes perceive them. All the "Scorp buddies" and attempts at one-liners from Sam and the gang in SS4 are written with the intent of being cheesy corny 80s action flick humor (which it does so quite well most of the time) whereas all the fart jokes and outdated references in other games seem to be written because the authors thought they were genuinely funny somewhere deep within the juvenile parts of their minds. That is to say, jokes in SS2 were written without a single hint of irony as it is what the authors thought to be actual humor, and it is that intent of these otherwise unfunny jokes that made them endearing to the players, like the innocence of a child laughing at peek-a-boo. Either that or the players were actually children when first playing through SS1 and SS2 who also found those jokes to be genuinely funny.

Anyway, that's why Siberian Mayhem needs to have wild animals in the game again. It doesn't even need to be in gameplay or have AI; all it needs is a 3D model and can be hidden somewhere as a secret just so Sam can find it and say "Hey look, a mongoose!".