Yes, really. See the first video below.
A Perry Mason promo, aired DURING “The Mighty Mouse Playhouse”? Conversely, I wonder if Mighty Mouse was equally cross-promoted during Perry Mason. Somehow, I doubt it!
And, while we’re still in a “Mighty Frame of Mind”, play the color version of the complete, original Might Mouse theme song from 1965. Enjoy.
"Mouse v. Mason"