Failures and mistakes, relationship friction, increased pressure and ticking clocks, loss of control

The character doing something silly that results in their arrest 
Changing a family member's clocks on April Fools' Day, causing them to miss an important job interview
Throwing a flaming bag of poop on someone's doorstep and the porch being burned down
Replacing the office treats with marijuana brownies the day before a random drug testing
Setting up a prank for a friend and it backfiring on someone else
Moving or decorating someone's car as a prank and damaging the paint job
Organizing a hazing ritual that ends in someone's injury or death
Participating in an insensitive prank that is shared online, resulting in backlash and a permanent record of the character's ignorance or racism
Telling a lie that is taken as the truth, causing widespread hysteria or panic 
Messing with a friend's car so it won't start and them being mugged while walking home

Having to apologize for a prank
Being suspended from school or reprimanded at work
A relationship with a friend being damaged because of the prank
The prank causing property damage the character must pay for
The character developing a reputation as a prankster and no longer being taken seriously 
Innocent bystanders being harmed by the prank
Having to be hyper-alert to avoid retaliation
Being publicly humiliated as people share what happened on social media
The character being pressured by their peer group to orchestrate more pranks
Being monitored more closely at work or school because trust has been lost