When Donald struggles with the connecting rod of one of the pistons in "Tugboat Mickey" from 1940, it at one point hisses back at him when he says something and Donald getting angry at it is similar to "Clock Cleaners (1937)" from 1937, where a spring hisses back at Donald when he says something and Donald getting angry at it. Both say a few of the same lines as well and cause Donald similar trouble at the end of their interaction.
The ending of "Tugboat Mickey" from 1940 is similar to "Boat Builders" from 1938 where the boat gets destroyed and causes Mickey, Donald and Goofy to land in the sea, even with broken boat parts next to them.
"Tugboat Mickey" from 1940 is the final of five Mickey Mouse Boat Cartoons and thus the final of three Mickey Mouse, Donald Duck and Goofy trio Boat Cartoons ("Boat Builders (1938)" from 1938 and "The Whalers (1938)" from 1938.). It also is the only Mickey Mouse, Donald Duck and Goofy trio Cartoon, featuring all of the Characters modern designs, especially Mickey who has his current redesign, not counting the "Mickey and the Beanstalk" segment from "Fun and Fancy Free (1947)" from 1947.
The assumed distress call Mickey, Donald and Goofy receive from the radio, in "Tugboat Mickey" from 1940, is about the sinking "Good Ship Gigantic", which is a parody of the "RMS Titanic" that was the largest ship afloat at the time she entered and actually sank in 1912, after only five days of operation.