Denial during a scene helps nobody and it is uncomfortable as hell for your audience. I need to make a lesson about taking care of your audience, because there is some serious neglect going on here. #SavetheAudience2k15.
Let's begin, as I usually do, by analyzing the problem. Because improv is, of course, made up on the spot, players do not enter the scene with a clear, thought out idea of what is going to happen; however they do typically create a general scheme up in their think tank. With mere seconds between suggestion and scene, each player scrambles for a witty, working opening, and this is where the denial starts. That moment when the scene begins and you're just about to give your opening line, your scene partner jumps in with something in another realm. "Hi, welcome to Spacy's!" Your mind is scrambling, you're gasping for breath. This was not how it was supposed to go, you tell yourself. They're looking at you expectantly, your nanosecond of thought is running thin. What do you do, what do you do? You're so shot down you can't think! It's like your brain only accepts one thing and only that thing, so you blurt it out: "What are you talking about? I work here, idiot."
Your scene partner's eyes widen, the elders in the crowd shake their head. You've blown it. You left him behind on enemy lines, soldier! Have you no shame? The guilt fills every part of you as they start blubbering, grasping at vowels. "S-Sorry, we j-just haven't had a customer in so long," they say, altering their character from the spunky (maybe too helpful) employee to the dumb, bottom of the barrel coworker. You have managed to both grab the crown and have it thrust upon your head at the same time (Shakespeare spins in his grave). You want to turn back, but you can't now - you've made this bed and now you're going to sleep in it. Who even is your character? It's not what you had in mind, either. No one is happy, and it is all your fault.
You may think that sounds a tad far-fetched, but I have lived the nightmare. Improv Denial is the player not responding to the facts presented to them, in short. This can range from walking through a table clearly set up multiple times, to not letting your partner do what they want (like above), or just blatantly disagreeing to the point that it leaves comedy and becomes a rocking chair (in other words: it's something to do, but you're not going anywhere). And the three biggest fuels for denial are Long Range Thinking, Ignorance, and Nervousness.
Long Range Thinking
One of the biggest issues in my above scenario is the players both trying to sculpt the scene before it even started. The best improv truly is line for line, and troupes should exercise the habit of basing their line off of their partner's last line. .When you start entering scenes with an idea in your head, rejection (or, you know, the other player not reading your mind) becomes harder to face and get over, causing that "I can't think of anything else now" spasm. Some improvisers try to avoid long-range thinking by starting a scene with a clear head. Establish a ghost of who you want to be, but allow that to adjust to who your partner comes in as. Group mind is important here, the bond warding off awkward "who starts the scene" jitters that lead to pre-planning. But the most proactive tip is to set up your scene versus jump in with dialogue. Spend a second observing each other in silence while setting up your location, and project to each other who you want to be.
Newsflash! Ignorance is anything but bliss when it comes to improv. You need to be on top of your game when it comes to a scene, because if your partner mentions their dog named Sparky you best remember that like it's the golden gospel. We can't be having you calling my chihuahua Rover halfway down the road, son. Yes! plenty of denial comes from the players just not knowing what the hell is transpiring around them; not listening, forgetting important stuff, or being so wrapped up in their improvising that they don't even notice the scene stopped moving and fell asleep at their feet. Rocking chair, amiright? You recognize these types because they're the ones calling Clark 'Robert,' they're the ones walking on your desk, they're the ones saying, 'Well of course I can't be the robber! Even though you established you aren't, and so did the only other person on stage in this scene. I'm not, but maybe you actually are, because I didn't hear you basically paint the crime scene with my DNA a little while ago. Sry.' I can only help by telling you to set an example. Always be aware, listening, even if you're in the back. And don't be afraid to call a brother out.
Nerves get the best of us sometimes. Improv is no exception. In a moment of fear and loss of brain activity, you may just start asserting what you want and know onto the scene. This part comes with the long range thinking and ignorance as well, but can some what stand alone. Maybe you just don't want to be the bad guy, or you know that the direction of the scene is not something you can handle. Maybe this is all going way over your head. When the scene is moving at one million miles a minute and your brain is drawing blank after blank, it becomes harder to accept the facts and go with the flow. Instead, you start calling decisions, thinking blindly and trying to follow your own plot. Soon enough you've derailed it. Beat this beast by calming down and not being afraid to take a moment of silence to think (of course not an awkward one), and learn to live with not getting your shining moment. Sometimes you have to be the bad guy, idiot, or simply the guy who is dictated by everyone else. You have to be able to accept that sometimes.
You and your troupe can treat a denial problem with a rousing game of The Denial Game, and Dan Goldstein recommends simply (in rehearsal, and nicely) calling your scene partner out by meeting their denials with, "There's no denying that!"
Of course, make sure your troupe knows that some denial is okay. You know, comedic denial. Denial that isn't actually denial. Like one-up dialogue (ex: "My sword is the sharpest in the land!" "In the land? You obviously don't import your swords!" DG) because that's denying that something is that thing, without totally wrecking what they've said (ex: "Well your sharpness certificate lied so ha."). There also may come a time when your character needs to say no. Just remember, "No, but" is p much "Yes, and" (some people don't get this - but that's a story for another day.).