regarding big jerry's BOUNCED check at the bodega...
marcelino has jerry's check TAPED to the cash register right in plain sight of each customer (within inches).
KRAMER notices right away that it's seinfeld's check "it's the only way you'll learn"
GEORGE notices too - "i see you chose the clowns with balloons..."
ELAINE can only offer "some moron bounced a clown check" - she apparently has NO clue that it was jerry's. if i noticed the design, i'd look and see WHO it was!!!
ELAINE, therefore may be the doofus.