Season 5 or 6 or 7 AU

What with Sunnydale's death rate not only do students die but so do professors sometimes. So Sunnydale U has a high teacher turn over rate.

One day Spike, needing money, finds out that the University desperately needs a poetry professor but can't find one. So with fake papers and a knowledge of poetry Spike fakes his way into the job.

He is instantly a hit amongst the students, especially the female ones. After noticing Spike's absence (he's working) Buffy automatically assumes the worse and starts hunting him. She finds him on campus surrounded by female admirers hanging on to his every word. 

She does not like this at all!

Spike might have also been saving a few of his students on campus earning him hero status also. 

Bonus Points. .....when on campus Buffy gets irritated when one of Spike's young female admirers looks at her than ask Spike who the "old" woman is.