The Custard pie is an item in KQ5. The custard pie looks delicious, yum. It is used to kill the Yeti. The pie can be eaten, making the game unwinnable (eating the pie will also result in a loss of points, indicating that it was used wrong).
Custard Pie was the last type of pie that the Baker Bros. had to sell at that time in the day. Custard was Graham's favorite kind of pie (but when it came to pie, all kinds can be considered Graham's favorite).
Graham didn't know how he was going to defeat the yeti, and was feeling a bit peckish before he entered Yeti Cave. He thought if he munched on a bit of pie it might stimulate his mind. He pulled out the pie to look at it. Unfortunately it had not travelled well, while it still had its oval shape, it had become dented and smeared. Even to Graham, whose sweet tooth never saw a pie he didn't like, found it unappetizing. At the moment as he was staring at the pie disappointedly, the snow monster arrived on the scene. Announcing its arrival with a roar, Graham's attention switched to the beast. His action was total reflexive, startled he jumped at the roar, and flung the only thing in his hand in the direction of the attack. Graham's aim was good, as good as his aim had always been, it splatted in the Yeti's face. The Yeti never knew what hit it, as it stumbled blindly over a cliff to its death.
Without realizing it, when Graham was confronted by something big and ugly, he had tried a bit of slapstick comedy and did what Soupy Sales would.
Behind the scenes
This puzzle is inspired by the classic trope of throwing a pie in someone's face in early comedies.