"...so that's why I hate checkers. Anyway, behold! The chess-iator! With it, I can replace every game of checkers in the Tri-state area with a game of chess! Now, chess, that's a good game, not like checkers at ALL…"
As soon as his nemesis had finally revealed the day's -inator and it's function, Perry started to search for a way to escape his trap (it was a platypus-sized chess piece - a black knight, to be more specific. Doofenshmirtz had made a Batman-related joke that shall not be dictated because of copyright violations due to the fact that Disney does not own the DC comics universe. Which is pretty sad, because they would have done Robin more justice than Cartoon Network has.) Eventually, Perry realized that the chess piece had a sticky game piece bottom rather than solid … whatever chess pieces are made out of, and could be quite easily removed if he just applied pressure, which freed his feet. Doofenshmirtz comically didn't notice when a platypus-sized chess piece waddled by him - until he realized it was heading towards the self-destruct button.
"Perry the Platyknight, you get back here!" Doofenshmirtz lunged at Perry, who ducked, which sent the doctor over his head. There was a series of crashing sounds, involving screeching tires and a cat meowing, Doofenshmirtz, who didn't seem to have learned his lesson the first time, lunged at him again. This time Perry hopped at the last second, landing on top of Doof's upper back. He crossed his legs around the doctor's neck and twisted, slamming the face of his enemy into the floor.
"Oww… I'll get you for that!" Doofenshmirtz caught the platypus off-guard by flipping over, resulting in Perry (still in the chess piece) lying on his back on the floor, with Doofenshmirtz on top of him. However, the Doctor had miscalculated Perry's initial distance from him, and his face had ended up at a closer proximity to the Platypus's face than expected.
Now, the duck-billed platypus has a rather strange and interesting anatomy, full of unusual quirks that make the creature so unique. One of the most prominent parts of their anatomy is their bill, which is full of many interesting attributes. First would be the texture, which unlike the hard bill of a duck, is rather soft and rubbery. This is because the bill is covered with millions of tiny sensitive button-like structures, which allow for a sixth sense. This sixth sense allows the duck-billed platypus to navigate murky waters, and find prey. To find the prey, the bill not only senses the form of the creatures they eat, but also picks up on the organic electricity that allows basic bodily functions needed for the survival of all organic life within the kingdom Animalia. This lead to a rather interesting experience for both parties participating in the unexpected kiss. Perry had always known that his nemesis's organic electricity was above average, most likely a result of high brain activity - an attribute he took advantage of often when trying to locate the man. However, to have all his sensors pressed simultaneously, with one of the parts of the human body with the thinnest skin, by a man with an already unusually high level of organic electricity, was a sensation that was almost overwhelming. For the man, however, it was not sensation that overwhelmed him and kept him frozen. While this was, indeed, Perry's first kiss, the scientist had numerous romances in his past, and while most of those romances ended horribly before they even really began, the man was not alien to the feeling of lip contact - although he could honestly say that this was the first time he had ever kissed a platypus. No, it was shock that had kept him frozen, along with a small dash of wonder. Who knew that bill was so soft, that it had so much give to it? Sure, it was a little cold, but that seemed to make it better somehow, and it might be kinda slimy, which was totally gross, but also kinda soothing, and…
While the evil scientist was caught up in his internal monologue, the secret agent struggled to unfog his mind enough to do something. It was really hard to think straight enough to shove his nemesis off, though, through the explosions of chemicals and chaos of NEW that was surging through him. Eventually, though, he gained enough hard-earned resolve to lift his hind legs and plant a firm kick in the self-proclaimed doctor's chest. Doof flew backwards, and Perry used the momentum of the kick to swing himself into a recuperating kneel disguised as a fighting stance. Doof stared at him with a slightly dazed "WTF JUST HAPPENED" expression on his face while Perry hid his face with the fedora, not trusting his eyes to form a glare while he tried to regain his dignity.
"Uhhh…" Perry leapt forward, kicking his nemesis in the face, and the fight resumed as if nothing had happened. That day, Phineas and Ferb's giant checkers arena, played using UFO-like hovercrafts, was turned into a giant chess arena and stolen by ancient French soldiers just as Candace and Stacy arrived, after a small adventure involving a ducky momo fanclub that wouldn't let Candace join. Just an average day - but, like many average days of that summer, things changed, if only slightly. Like the day that Carl met Monty, or the day Candace subconsciously decided that her brother's safety and companionship was far more important than any bust, or the day that Buford realised how horrible a wedgie felt, or the day Isabella decided to simply accept Phineas's friendship for the time being and started truly being herself around him rather than desperately trying to get his attention, or the day that Irving became a friend rather than just some creepy fanboy, or the day Buford stopped being a bully. Some of these changes could be tied to a single event, but most happened gradually, through not one, but many days. But most times, coincidence was a needed force to push everyone in the right direction - coincidences such as this one, where lips met bill in the heat of the battle, and they each had something more to contemplate when wondering about each other and the strange relationship they had.