Round red rock
From the Super Mario Wiki, the Mario encyclopedia
The round red rock is a circular-shaped toy block that Wario can ram in to move along to an area where he can stand on top of it. This round object lets him access places to grab coins or Diamonds. The only stage that round red rocks can be found on is Toy Block Tower, in the Topaz Passage. It behaves similarly to Chomp Rocks from the Yoshi franchise.