Tad and Dad by David Ezra Stein
Tad the tadpole spends every day with his awesome dad, and shares a lily pad with him at night. It's always been that way... but little Tad is growing up, and quickly becoming as awesome - and large - as his dad. As his new parts sprout, he's learning to swim and hop and croak just like Dad. Dad is very proud, but when Tad's accomplishments carry over into night time - bringing lots of kicking and croaking in his sleep - the lily pad is no longer a bed for two. Even Tad finally realises it's time for a lily pad of his own, and all is well - at least until Dad realises how much he misses Tad.