Fetty Wap's son had the best birthday in the galaxy ... shutting down an entire fun center for a 'Star Wars' themed bounce session.
Sources tell us Fetty dropped 5 stacks to rent out BounceU in Paramus, NJ for Aydin's 5th birthday party ... making the entire place VIP only.
We're told around 50 kids showed up for the bash, which included cosmic bounce houses, cotton candy, face painting, balloon twisting, tons of pizza, and a mobile video game trailer.
For dessert ... a two-tiered Stormtrooper cake complete with fondant light sabers.
Lucky his son is.