The letter y

The yellow yak is yawning - y-y-y mime stretching and yawning, repeat 3 times

The yellow yoghurt's yucky - yuck, yuck, yuck

make face
The yellow yolk is yummy - yum, yum, yum rub tummy
The yellow Yorkie's yapping - yip, yip, yip jump up and down
The yellow yak is yodelling yodel away!