Which mouse made its first appearance in the 1953 cartoon "Cat-Tails for Two"?

"Cat-Tails for Two" is a 1953 Warner Bros. Merrie Melodies cartoon, directed by Robert McKimson and written by Tedd Pierce. The short was released on August 29, 1953. It was the first appearance of Speedy Gonzales, in a prototype form. Because this cartoon's rendition of Speedy Gonzales looked rather coarse, they redesigned him for future cartoon releases. The cartoon has been criticized for its stereotypical and insensitive depictions of Mexicans.

The two cats pursuing Speedy in "Cat-Tails for Two" are the slow-witted (and injury-causing) Benny and the fully functioning but unfortunate George, both patterned after the characters Lennie and George in the novel "Of Mice and Men". George and Benny are walking down a pier looking for food, when they find a Mexican ship. Figuring the ship will have plenty of Mexican mice, i.e. "Mexican food" (Benny: "It gives me the heartburn and I love it!"), they climb on, only to find an unkempt mouse calling himself "Speedy Gonzales: The Fastest Mouse in All Mexico".