Im still suprised no one uses him alot. Everybody is so combo-thirsty for things similar to melee, and diddy can somewhat bring it (or at least as much as you can in brawl). He can do so many amazing things and even out alot of seemingly bad matchups, but you have to be creative.
First the pros of diddy. He is pretty fast, both running and attacking. None of his attacks have much noticable lag before or afterwards. Especially his dsmash, which is almost as fast as Mario's and Wolfs. He has a great aerial game, with both a bair that can be done twice in a short hop, and a fair thats a kill move. Couple this with his amazing recovery, both with his chargable upB that can reach from off of the screen on FD back to the ledge,and his side B (which you can still do an upB after a sideB), it makes him one of the best chasers. he also has three spikes (dair, sideB --> jump, upB). I'd also like to note that his throws have some great knockback, especially fthrow. On the ground, his bananas have the potential to pretty much determine any match by themselves. Diddy can make insane Lucario-type comebacks with proper use of two bananas to keep an opponent slipping. For his speed, he has great killing power. And most imporantly, hes an adorable little monkey. Cant go wrong there
For cons, he has two big ones. First is his approach. Without a banana, diddy's approach game is both terrible and easily punishable. If an opponent is just standing there and not on their *** from a banana, both of diddy's approaches (dash attack, sideB --> kick) are easily shieldgrabbable. Even worse is if you try a SHFair and its blocked. While it doesnt have any noticable lag in the air, it has a lot of afterlag if you land on the ground before its finished. In fact, every air move except bair has afterlag if you lag on the ground before its finished, but these moves shouldnt be used as approaches on ground characters anyway. Another con can be his bananas. Any smart person will eventually figure out how to use them against you. This is terrible at the time, but great for the long run. Eventually as a diddy player, you will run into enough players that try to use your bananas against you that you will learn to avoid your own bananas when someone else is using them. It helps that diddy can get his bananas back in many ways:
-Just instant dash attack (slam control stick then c stick to dash attack as soon as you move) when they throw it at you, if you are running, a dash attack will catch a banana thrown at you. You can dash attach either backwards or forwards, depending on the trajectory of their throw
-Air dodge if you are already in the air. Any aerial will catch it, but i think air dodge has the largest window, could be wrong
His final con is range/priority. While his smashes are all quite fast, they dont have the greatest priority, and his little monkey arms/legs dont give him too much range (Aside from his ftilt, which is just awesome in range).
I think his best matchups is against anyone that doesnt have a reflector or great projectiles. This means that Diddy is in a bad situation against spacies, snake, and Pit.
One thing i wanted to talk about alittle more is diddy's killing power. Diddy has been graced with one of the best recovery and aerial games in brawl. For this reason its that diddy's ground smashes weren't made to kill right off. If you want to kill with diddy, you absolutely have to chase, and with the tools you have been given, there is no excuse. At any decent percentage, you can kill by simply dsmashing/fthrowing them off of the stage (since they have the best horizontal trajectory), then going out and doing whatever you feel like basically. You are equipped with 3 different ways to spike them, a fair thats insanely fast and is probably 2nd-3rd overall his his horizontal trajectory moves, and a recovery game that will get you back to the stage from almost anywhere. If they make it on the ledge, you can kill them when they are at about 60-70% by just stage spiking them like alot of chars can. for diddy, its just running off and bair them while they are hanging on the ledge and their invicibility frames run out. Thats not really char. specific though, but diddy can also do it. If they are really close to the stage, you can hang on the ledge yourself, hit back to let go, then do a jumping dair while DIing backwards to do a spike. You'll spike in an open space level and to the side of the ledge, and if you're fast enough you can DI back to the ledge without having to use any recovery moves. Facing a MK or pit that you just spiked but he's coming back with his 4-5 jumps? Hit down to let go of the ledge and then upB when when you are right above them. It will spike them and send you back up to the ledge. If you time it right (the letting go, the up B, the re-grab of the ledge) you will have invicibility frames the entire time.
The last thing i wanted to add was diddy's peanut gun. If this projectile was any better, Diddy would simply be overpowered. On a simple scale, it can do some ok damage when charged (17% when fully charged). Its best use comes from its aerial control. First, since its so ridiculously easy to catch an item while in the air, most of the time while people arent trying, you can shoot a peanut at them while your opponent is in the air and coming towards you. If they catch it, its over. Now they cant do any A-moves until they throw the peanut, and its a giant flag saying "Hey, look at me, i cant use half of my moves, attack me!". And if they dont catch the peanut and get hit by it, it opens a window for you to go and use an aerial attack (fair) almost immediately after they get hit by the peanut so they cant airdodge. But, possibly its greatest use is its aid in killing power. Simply, the peanut is a gimping machine. See Ike charging his sideB to get back? Charge your peanut gun and aim to hit him in the air while he is coming back, the peanut will hit him, and his sideB will stop right then and there. Of course, he can then still upB, but that wont do any good. See a falco/wolf/fox falling and getting ready to sideB? hit them with a peanut before they do it and they will usually drop below the line in which they can still side B so they will have to upB. If you get a space animal upBing to recovery, alot of the times they arent gonna make it.
Anyway, im done. I dunno if the official site-wide discussion is still going for diddy, but here's my part. In general, to be good with diddy, you have to
-Chase people. dsmash/fsmash wont do it alone until they are ridiculously high%. You have many ways to chase. dont be scared
-Glide toss whenever beneficial. sometimes its good to just regular throw you know, but learn to glide toss so you can do it when you really need to
-Realize the peanut gun was not made for damage. It was made for gimping recoveries and creating openings (making them catch it) for when you dont have a banana, since approach is a problem.
-Learn to regain control of your bananas. Because its stupid to think they wont gain control of a banana or two. Best method is instant dash attacks when you know its coming.
-Use two bananas. One is great, but get into a routine of using two. Also remember you can still use B moves while holding a banana, so dont be afraid to stall someone by shooting a peanut before throwing a banana.
-Be creative. Straightfoward the entire time isnt gonna work while playing diddy
-go to tourneys. That'll increase your skill level so fast its not funny