Dumbo the Flying Elephant Sightings
Chance the Rapper - I had no clue which one he was (not my music style) but I walked by his group a few times at Dumbo while I was moving strollers.
Michael Buble - He rode Dumbo while I was working, but I was on the OTHER side of Dumbo so I could just watch from afar.
Kenan Thompson (from Kenan and Kel) - I checked his seatbelt when he rode Dumbo.
Jenny Slate - I checked her seatbelt when she rode Dumbo.
Chris Evans - He was riding with Jenny Slate, so I also checked his seatbelt at Dumbo. I also saw the two of them exit the Barnstormer.
The Seven Dwarfs Mine Train Sightings
Trace Adkins - I saw him in the Mine Train exit when he was going up to ride.
Fifth Harmony - I saw them get on the Mine Train while I was working, but didn't know who they were until my coworker told me as they were about to dispatch.
Josh Gad - He was walking around the park after the park closed with his tour group and I told him to have a good night (not knowing who he was) then he was like "thanks, you too!!" and I was like OH THAT'S OLAF.
Dan Cockerell - I don't know if he counts, but I'm going to include him!! Dan is the Vice President of Magic Kingdom, and I got to meet him and actually have a conversation with him! I was in training and we went down to walkdown in the morning (where you walk guests to the different lands at rope drop) and before the park opened he was just wandering around and came up and talked to us! REALLY nice guy.
I think that covers it for who I got to actually see...I know that while I was working one day Jack Black rode the Barnstormer, Paul Rudd rode Mine Train, Brittney Spears rode Mine Train, and George Lucas rode Dumbo. I'm sure there were some others that I COULD have seen but missed due to bad luck. But that's a fun perk of working high-profile attractions! I'm sure you see way more in Disneyland, but it was cool for me! Makes for fun stories.