Left image: It is a text message asking the recipient to reply back once he/she returns home
Right image: It is a man sleeping on his bed with his phone on silent mode
The images are funny since they show how a sender wants the recipient to revert once he gets back home but the tired recipient ends up falling asleep completely forgetting about the message while the sender keeps waiting for a reply. The fact that the recipient leaves his phone on silent mode makes it even funnier since the probability of the sender being able to contact him becomes even slimmer.