Back-to-back Saturday nights at the L.A. Pittenger Student Center, and about the only things they have in common are free food and bowling.

That’s Late Nite at Ball State, the after-hours activity that has evolved far beyond its origins in 2001 as an initiative to provide students with an alcohol-free social environment. That year’s 12-week program, which drew about 3,700 students, has since expanded to 30 weeks attended by nearly 36,000.

From week to week, one Saturday after the next, it’s clear how different each event can be.

This semester, one Late Nite featured an honest-to-goodness petting zoo, a make-your-own teddy bear activity and — do you see a theme yet? — a showing of the movie “The Jungle Book.”

This weekend, it’s a road trip motif, with a take on the YouTube Carpool Karaoke sensation, make-your-own license plates, car snacks and, in a nod to Late Nite’s original mission, a chance to try on goggles that illustrate the perils of being impaired by alcohol.

Students plan and set up Late Nite based on a different theme each week, a strategy that can be seen in decorations, attractions and food.

“It’s become an event that’s a Ball State staple,” said Alicia Fitzgerald, who as an assistant director for Student Center Programs oversees Late Nite. “Students can come to Late Nite and participate in activities as a college student that you just don’t have the opportunity to do once you leave the college environment.”

Late Nite can be a great introduction to that environment, as pre-med student Tahjia Salmon found out.

“My initial experience with Late Nite was as a freshman,” said Salmon, of Indianapolis. “Everyone kept on telling me, ‘Hey, you should go to Late Nite. There’s free food. You can meet new people.’ I was like, ‘OK, cool. It sounds fun.’ ”

Salmon made lasting friendships and even joined the event’s staff before taking her current campus job, in the Office of Student Center Programs. During her 18-month stint with Late Nite, she often could be found putting up decorations and making sure everything was ready to go for the four-hour party’s 9 p.m. start.

Her motivation? She wanted to be a part of an experience that had made her feel so welcome when she was new on campus.

“I just liked how Ball State, the college that I went to, is actually creating a safe environment for any of the students who wanted to partake of it.”