make the groundskeeper wear his sun hat is the fourth listed mission in Untitled Goose Game, for the mission the Untitled Goose needs to make the Groundskeeper wear his Sun Hat.
How to complete[]
If the Untitled Goose grabs the Tulip in The Garden and then make the Groundskeeper put it back the Untitled Goose can grab his hat when he's bending down to put back the Tulip, then if the Untitled Goose runs to the grass the Groundskeeper will lose him and then go put on his Sun Hat.
get into the garden · get the groundskeeper wet · steal the groundskeeper's keys · make the groundskeeper wear his sun hat · rake in the lake · have a picnic · make the groundskeeper hammer his thumb
break the broom · trap the boy in the phone booth · make the boy wear the wrong glasses · make someone buy back their own stuff · get on t.v. · go shopping · trap the shopkeeper in the garage