Alternate universe
 

One day, a group of scientists switch on the Large Hadron Collider and in doing so confirm the existence of the multiverse. After some tinkering they discover that it is possible to step into the machine and be transported to one of these universes. After stabilizing it enough for use by the general public, they decide to charge a small fee for a trip to see your alternate self.

What do you catch your alternate self doing?

Posting on an internet forum.

Being a loser.

Then I punch him and tell him straighten up.

Depends on what alt universe/dimension Really
Hell for all we know we could meet Jenkins and his "friends"

Krylo.

I give him hell for not inviting me to his wedding.

Visiting another alternate self.

If we're talking about one of those everything is the complete opposite dimensions, then my alternate self would be outdoors drinking something diet.

My alternate self would then be a thin jerkass who hates sweets, shuns gaming and is crazy religious.

I (original 'verse) don't know what I (other 'verse) would be doing, but I (original 'verse) know I (original 'verse and probably other 'verses as well) will be killing me (other 'verse) before the other me (multiple other 'verses) get to me (original and first other 'verse) so that I (original 'verse) may consolidate all my (all the other 'verses) life force into one body.

Mine (original 'verse).