Stiles and Derek have an agreement, a gentleman’s agreement, if you will. And it’s actually worked out quite nicely, on multiple occasions, in fact. The agreement being that if the situation should arise where it would be necessary to have a significant other close by, they would step in and pretend to be that significant other.

Cover credit:SepticGirliplier At first Stiles didn't mean to intrude but now he finds it fun to crash Derek's lectures. Especially when his students gossip about Derek to stiles because they have no idea he's Derek's husband. But the longer it goes on the harder it is to hide from Derek while he teaches. But once Derek catches on to stiles's little scheme without him knowing he gets revenge on his oblivious husband.