Idea's for comedy sketches

As part of my PPD module I am going to be showing a step by step process of completing one of my targets. Originally the target was to re-write the script for a short film I pitched to my lecturer, in order to improve my screenwriting skills but she felt that there wouldn't be enough time before the end of the course and suggested a two minute sketch instead.

Anyway, here are my ideas so far:

• The lead singer in a rock band dies just before they are about to go out on stage. The rest of the band panics and wonders what to do, but their manager tells them not to worry and he has an idea. Cut to the band on stage, and the singers body is being puppeteered while his vocals are played on tape.
• A young woman is being chased by a masked killer. She trips over as he slowly moves toward her. She shouts "GO AWAY!" at him, after which he stops, removes his mask and says "That's all anyone had to say" before walking off.
• A "who's on first" type routine in which two friends argue over the title of the 1982 film The Thing.
• A man discovers that his wife is having an affair, but seems more upset her eating a chocolate bar he was keeping in the fridge than her infidelity. 

Once I have chosen the idea I will pitch it to my lecturer, and if she approves of it I will begin a first draft by next week.