Whenever I draw my little comic thingies, I realise that I tend to skip on the legs. Whenever I start working on a game and get a bit more serious about it, I leave the walkcycles as long as humanly possible, because I hate them. And don't get me started on hands, the most annoying thing in this universe one can decide to draw.
When you're working on your game, your imagination will often light creative fireworks that you just know you will not be able to animate, code, compose, or get for free from the interwebz. Your cast of thirty-seven characters, ten of them requiring full walk/talk/idle animations, your idea for a time-critical Guitar Hero ripoff, that puzzle where you need to align stars in real time, the cursor dipping into the picture as if it was wet paint... they sparkle in your brain, but you know they won't look that perfect on the screen. They may, in fact, look like crap.
Alternatively, you may have a rather minor character who needs one big animation, and realise that the amount of work for this small scene would be bigger than the rest of the game.
As a "lone wolf" who does all the jobs, you will often face a situation where you lok at the idea, the required work, your shedule, and then sigh and scrap the idea. Even if you're part of a team or have some connections to people who will help you out in a tight spot, you will often find yourself wondering if you can pull it off.
Fortunately, we can always... cheat. We can, by means of trickery and guile, create the ILLUSION that awesome stuff happens in our game without spending a lifetime to animate, script and coordinate it. Oh yes, we can. Hey, there are comics out there where the artist never shows the legs of any character. There's music that mostly consists of silence. There's games without a main character at all.
Behind closed doors:
You have a great action scene in mind. Your die-hard PI is going to meet a shady guy and beat seven different kinds of crap out of him. A fight to the finish, where things get broken and hijinx ensue.
You don't want to animate that at all- it's just too much.
So... let the PI enter a dark alley, effectively leaving the screen. Then, display dialogue. Make it good dialoge. Make the screen shake. Get some smackin' sound files. If your writing is good, the players will imagine just what you had in mind. And it might even be better than what *you* had in mind, because players love to see their own imagination.
You have a character who will, as part of a puzzle, leave his office/hideout/whatever so that the player can do something in the room. That means the supporting character will need a walkcycle.
Walkcycles are time-consuming...
Just place a convenient WALKBEHIND. You can then move the character without animating his legs; a slight movement of the head, 3 frames or so, may be enough to complete the illusion!
Explain It Away
A character has super-speed, is extremely nimble, a born acrobat. At some point his skills are needed to be shown. Animation again, and you are no good at speedlines and stuff.
What you want to show may look cheap.
Explain it away. A very fast character? Why, he is so fast that you don't even see him move! You ask him to show his speed by daring him to shuffle a deck of cards- then you play a quick rattling sound, and the character says smugly: "And I just did."
Works very well with speed; other special abilities may need better and more creative explanations.
Hide It In Clouds
The assembling of a complicated machine is required. Many, many small parts will be needed to animate, move, scale... You shiver as you think about it.
Don't show it at all. An old cartoon tradition is the Big Ball Of Dust: Have such a cloud and show the character's hands moving around it, and stop with the fully assembled machine.
Overuse of these tricks may result in a game that looks rushed and as if made by a guy who doesn't put his heart into it. Counter effect by adding a few elaborate scenes.