Final answer:
Stephano contributes to the plot of Shakespeare's play 'The Tempest' as a comic relief character and catalyst for conflict and mischief.
Step-by-step explanation:
In Shakespeare's play The Tempest, Stephano contributes to the plot by serving as a comic relief character and providing a contrast to the more serious and noble characters. He is portrayed as a butler who, along with Trinculo, stumbles upon Caliban on the island and plots to overthrow Prospero. Stephano's involvement in the plot adds humor and serves as a catalyst for conflict and mischief.