We have a very cheap but very inconvenient flight thru Chicago to Costa Rica.
We arrive in Chicago at 6:30 on Saturday evening and leave at 3 in the morning. We are looking for ways to waste a few hours - dinner, drinks, some late night interesting things to do that would not be too complicated.
Any suggestions?

Assuming your flight is on-time, you can take the CTA Blue Line train into The Loop. The trip will take you about an hour and will cost $2.25 each way. Follow the signs from the baggage level.

You can have dinner and walk along Michigan Avenue or in The Loop. There are literally hundreds of restaurants in the Mag Mile/River North area. Check www.chicagoreader.com for ideas. You can search by neighborhood, price or cuisine.

Depending on what time of year, Navy Pier has fireworks during the summer months. Check their schedule at www.navypier.com. There are several spots to view them.

There are a couple movie theatres around the Mag Mile if you want to do something a bit more subdued.

The Blue Line runs 24-hours but is sometimes closed for construction in certain areas on weekends. Closures are usually announced by Thursday for the upcoming weekend. Check the CTA site at www.transitchicago.com. If service is suspended, there will be shuttle buses to replace the trains. Just allow for some extra travel time to and from the city.

I would probably just head to the O'Hare Hilton - it's right IN the airport, with several restaurant and lounge areas. You could even look into checking into a room for a few hours' sleep. I'm not sure I'd want to wander around all night and worry about getting back to ORD on time for a 3am departure.

I think that I would bring a good book and do the Hilton also.

I would head into the city if there was enough time. You don't necessarily have to go downtown, by the way. You could take the train to Wicker Park and Bucktown, which are right on the blue line. Or you do a train/bus combo and be in Wrigleyville, Lincoln Park or Lincoln Square in an hour or less.

Agree with Wicker Park and Bucktown -- ton of restaurants and bars -- 20's-30s crowd. Blue Note and some other small clubs for live music on Milwaukee.

Big Star is Chef Kahan's (Blackbird and Avec) new haute "streetfood" concept although weekends will have a long line -- pork belly tacos, el pastor, etc. Only a few dollars a taco -- atmosphere not relaxing though.

45 minutes ORD-Damen Stop. If you get back onto el by midnight you'll have time to spare if you already have your BP to CR.

The OP does not say anything about carry on luggage. If in fact s/he has carry on luggage then it wouldn't be very convenient to travel on the train and then walk around Wicker Park area or downtown. There is no luggage storage available at O'Hare.

I got lucky once and after "tipping well" the bell desk captain at the O'Hare Hilton, he stored my carry on, but when I tried it again some months later, no "tip" would convince the man working the desk that day to help me out. I dragged my laptop bag with 2 laptops into the city because I wanted an Italian beef sandwich and meet up with some friends. I survived, but the bag started to get very heavy towards the end of my visit around downtown Chicago. I would not do it again.

Anyways, how about a fairly inexpensive cab ride to Muvico, a movie theater on steroids. It's located in Rosemont, right next to the airport. It's a beautiful facility, the latest projection technology, 18 screens, a full bar and a very good sit down restaurant, Bogart's.

Enjoy a nice dinner, watch a movie (I would suggest the VIP section) only people over 21 are allowed in, full bar, and restaurant reservations is provided for anybody buying VIP ticket. Latest Hollywood movies.

https://www.muvico.com/default.asp?t=210