From the end credits:
(image mirror)
I think bouncing up and down on the elephant's head is the mouse.
Fun little detail.
elephant and mouse
Re: elephant and mouse
Yeah, and it looks like this elephant is not afraid of mice. Or...
The mouse also appears on another picture from the ending: And in the Turbo Duo / PC Engine version:https://allthetropes.org/wiki/Eek!_A_Mouse!#Real_Life wrote:If a mouse is brought close and shown to an elephant, however, it's generally not alarmed in the slightest, and may even lift the rodent in its trunk for a better view.