I'm a bit dense.
Is the joke that they're excited to sit and block everyone's view?
Yep.
Could be about the children in the second row. Referencing that children in the front row can often make noise and otherwise be distracting, so the tall ones are glad to get the chance to ruin the kid’s experience specifically. Looks like all the other seats are filled, so it’s not like the tall ones are choosing the spot to block the view. They’re taking what was left for them.
It's a metaphor: tall people are inherently evil
Because some don't get these, here is an explanation. The three tall happy people are about to sit in front of the three small happy people. They are looking forward to the show. The small people will not be able to see. The tall people may feel bad.
This is funny as it is a shared experience. Must people that have been to a theater have either had things blocked by tall people (or big hair/hat), or have been the tall person.
It seems that the tall people are happy because they are gonna sit in front of the short people since the red tall one is pointing at them wiith a grim smile, like if hes aware of whats gonna happen.
The old "Man's inhumanity to man".
Ok, but what's the hidden meaning?
The world will end on the third day of the tallest month.
