2Yo Good Sleeper Now Waking up Crying Around 2 Am - 4 Times This Week!

I don't know if y'all have the answer, but I am hoping something you guys say sparks some grand idea about how to fix this.
BACKGROUND INFO:
My son has been a great sleeper thru the night since he was about 10 months old. He's been out of his crib for a few months now and hasn't rolled out of bed since the first week he was in it. He goes to bed easily and doesn't get out of bed to play around.
THE PROBLEM (sorry to be so long and detailed. I am hoping you see/read something I don't see):
The problem is that Thurs he woke up at midnight, came to our room, I guided him back to his room, told him "night night time." and he fell back asleep. Friday he woke up crying, came to our room, etc, and this went on for 3 hours! He'd stay in his room for about 20 minutes, then come back to our room crying. Needless to say my hubby and I were exhausted Saturday! Then Sat, Sun, Mon all was fine. Tuesday night he did the same thing. Since my husband had work the next day (I'm a SAHM), I didn't want to do the whole back and forth from his bed to my bed and crying thing, so when my son woke up around 2am, I laid on his floor next to his bed until he fell asleep. It took an HOUR and a HALF for him to go back to sleep. He wiggled around in his bed, a couple times he whined "mama" and I put my arm up to touch him. I went back to bed after he fell asleep around 4am and then he didn't wake up again till 7:30 or so. Wednesday night fine, then last night Thursday, the same thing. Again, my hubby had work early the morning, so I laid on the floor by son's bed for an hour till he fell asleep. I ask my son "Why are you crying" and one night he said "boo boo" and when I asked "where?" he said "leg." One time he said "head." Then for last night, he said "Noise" (Wed night there was a bug outside his window stuck between the glass and the screen and it made a loud noise. We fixed it and he slept fine thru that whole night).
MY IDEAS:
We've tried telling him if he says the whole night in his bed, he gets juice in the morning for breakfast (we mormally only give it in the afternoon after his nap). He liked getting his juice on the good nights. He didn't seem to care about not getting it on the bad nights. I've thought about getting a white noise machine, but I know my son will press the buttons and probably mess it all up. His room is a little louder with road noise (louder than my room). But we've been in this house for a year now, so he should be used to it. He doesn't have any caffeine during the days. He has one regular 2 hour nap during the day.
THE QUESTION:
So what else am I not considering? Is this an "I want mommy" phase? I don't want to be angry with him if he honestly doesn't feel good. But he's eating okay and doesn't complain about anything during the daytime. Maybe it's gas? His poops have been pretty hard. Maybe something going on there? What do I feed him to soften his poops? I've had a nightlight for a LONG time. The other night I noticed it cast shadows on his wall. Maybe he was scared, so I turned off the light. He doesn't seem to care either way. He will turn it on or off if he wants to. He has not seen any scary movies. Just the same old Toy Story 1 and 2 about 20 times each. He hasn't seen Monsters Inc even.

I appreciate all your ideas. I do not want this to become a habit. That's my biggest fear. His hard-wood floor is not comfy to sleep on, nor is this helping my mood the following day. Without good sleep, I am a grumpy mom. I do not want him to sleep with me and hubby, as I know I will not sleep well and that's just not the way we want to raise our kiddo.

UPDATE AFTER 4 ANSWERS:
He has some plush animals that he used to let sleep with him. Now he tells me "no" and throws them on the floor. He only wants his hard Buzz Lightyear toy in bed with him. When I put him back to bed during these awful nights, I remind him that Buzz is there with him and put Buzz right next to his pillow. I like the Christmas lights idea. Thanks. A fan - something we could use in Texas anyways. That would be a good one for him to stay cool PLUS the noise. His overhead fan is not loud enough unless I turn it on higher, in which case it's very squeaky. A fan on top of his dresser might do the trick. Molars -- I think he has them all. He got his teeth early. I just counted. He has 10 teeth on top, 10 on the bottom. Looks like they're all the way through. Perhaps I can take him for his first dental visit soon. A gate -- my mom brought me a baby gate today. She had some in her closet. I think that if he wakes up, he will stand at the gate and cry. Our house is very small. It's probably only 10 paces from his doorway to our bed, so if he cries for 40 minutes my husband will go bezerk. I will try the matchbox cars idea. I will try anything. I need to run to the dollar store and get new goodies. Thanks everyone!