Possible Clues:

• Spot was playing in the children's playground
• Up and down, present and past, in visible fashion
• Look and looked at its teeth going up and down
• Look and looked going up and down
• Children's up-and-down game with plank over barrel
• Notice looked at in the children's playground
• Perhaps in 12 across in the present, in the past, in the up, in the down
• That might visually go down and go up
• Notice tenses keep alternating
• Just look at the way 20 down goes up and goes down