Perhaps you could draw an octagon on the MDB, which should be very easy with the grid. Then write the word STOP in square block letters. (Again, using the grid.) Now erase the letters for STOP and explain that if a crossing guard is there you should obey the crossing guard. You will know them by the orange vest or the STOP sign they carry. Then you can draw the eyes, mouth, etc. and the top portion will become a hat.
For the special effects board draw a Yield sign and explain how that is different from a stop sign. You have to look to see if anyone is coming. (Then do a look, don't see with Oscar or the rabbit.) It keeps disappearing when you turn to look.)
My favorite joke: Before crossing the street you need to look both ways!
Puppet: Yes. Look up and then look down!
Current Topic - Design Ideas for the MDB and SFX for ROAD SAFETY