Games like ZooSim
Games like ZooSim include Undertale, The Stanley Parable, Slime Rancher, Jazzpunk: Director's Cut, and Outcore: Desktop Adventure. We matched them by the tags players give ZooSim on Steam (Surreal, Funny, Story Rich, Dialogue Heavy, and Comedy): closest matches first, and among equally close ones the better-known games.

Undertale
Shared: Story Rich · Funny · Multiple Endings

The Stanley Parable
Shared: Comedy · Funny · Indie

Slime Rancher
Shared: Cute · Funny · Exploration

Jazzpunk: Director's Cut
Shared: Surreal · Comedy · Funny

Outcore: Desktop Adventure
Shared: Story Rich · Comedy · Cute

OneShot
Shared: Story Rich · Cute · Indie

Firewatch
Shared: Story Rich · Adventure · Exploration

Bugsnax
Shared: Story Rich · Comedy · Cute

Psychonauts 2
Shared: Story Rich · Comedy · Funny

Otaku's Adventure
Shared: Funny · Multiple Endings · Story Rich

Lost in Play
Shared: Funny · Surreal · Story Rich

A Hat in Time
Shared: Funny · Cute · Colorful

The Henry Stickmin Collection
Shared: Funny · Comedy · Multiple Endings

Botanicula
Shared: Funny · Story Rich · Colorful

The NOexistenceN of you AND me
Shared: Story Rich · Multiple Endings · Surreal

DELTARUNE
Shared: Story Rich · Funny · Comedy

Turnip Boy Commits Tax Evasion
Shared: Funny · Exploration · Story Rich

BLACK SOULS
Shared: Funny · Story Rich · Cute

CHUCHEL
Shared: Funny · Comedy · Colorful

DEEEER Simulator: Your Average Everyday Deer Game
Shared: Funny · Surreal · Exploration

There Is No Game: Wrong Dimension
Shared: Funny · Comedy · Story Rich

Finding Paradise
Shared: Story Rich · Funny · Adventure

Wandersong
Shared: Comedy · Story Rich · Funny

OMORI
Shared: Story Rich · Multiple Endings · Colorful