My grandfather hanging out with Albert Einstein, especially the time Leo Szilliard showed up at the door to ask him to write a letter.
I’m off to ten years ago so I can see my wife in her suit on her way to work getting attacked by nesting birds outside her office near PacBell Park and running and swatting at them while they pecked at the back of her head and she ran inside the building to find the security guard laughing his ass off.
(Re-reading that it sounds cruel but we both laugh about that event all the time and I’ve always joked about how much I would pay to see a video of it)
My dad was a pint-sized tough guy in his youth. He stood about 5’ 8" and weighed all of about 140 lbs. when he and my mother got married. (FTR, she weighed 80 lbs. People were smaller in 1960.) Anyway, it was around that time that dad and mom and another young couple went out to a local road house to drink a pitcher of beer and have a pizza. They ran afoul of some greasers who made lewd comments about the women. Dad ushered everybody out the door and into the car. They took the women home and then dad told his buddy to get back in the car as they were returning to the road house. His friend expressed curiosity as to why they would want to do that and Dad explained to him that those greasers could not be allowed to speak so crudely to the women that way and not be called to task. So they went back. Decades later, Dad’s friend described the situation to me at my Dad’s retirement party. He described my old man as boiling out of the car and jumping on the nearest greaser “like that tasmanian devil in the cartoons.” Several independent witnesses also present at the party confirmed that Dad beat that guy and his two friends down in a just a few moments of terrifyingly intense violence. Dad’s buddy admitted “I didn’t do much but jump around and squeal.”
Dad was LE for about 40 years in one agency or another and he always had a rep as a guy who could handle himself in a fight. But I would really, really like to see my short, skinny father in his chinos and penny loafers go medieval on that trio of mashers.
I’m gonna sorta cheat: I’d want to see my biological parents saying goodbye to me b4 I was left to be adopted.
Shoot. If we could be corporeal, my pick would be to go back to 1995/96 and see a Marilyn Manson concert and party with the band 
before they got hugely famous. I count myself as “knowing” them, since I was two rows away from both Manson and Twiggy earlier this year (kiss my butt; that totally counts). Hell, I’ve talked to Daisy on Facebook before, that’s good enough. It seems like such an awesome party and this was before they got into hard drugs, at least if we can believe Marilyn Manson himself – mind you, they were doing *some *drugs, but more “exotic varieties of weed” than cocaine and heroin in 1995-ish.
My father’s Bar Mitzvah.
I would go back and watch my wife having sex with someone else before we met, but she says that it was never any good. Judging from the first few months of our sex life together, I believe her.
Instead, I would go back to see if this douche bag named Eric was telling the truth when he said that he had sex with the girl I was in love with in high school. If he did, show me. If he didn’t, show me what did precede him telling me that.