Jiggler v Boozer - 45:55 - Boozer's favor.
Bowser is a very interesting character with a ton of defensive tactics in order to keep approaching characters at bay. In this matchup, Bowser will not be approaching you by any mean of the word, he doesn't have to, and better yet, will not want to if he doesn't wish to get juggled. Jigglypuff will have to use her aerial mobility in order for her to get inside of Bowser and begin to abuse his blind spots, weight and general lacking in speed. Equipped with bair, pound and fair, Jiggs can definatly put the hurt on Bowser, using pound to beat out angled ftilt (when you space correctly) and bob him up slightly, where you can proceed to juggle him with uairs, bairs and finish with a fair at higher %s.
This is a major factor in this matchup, do not even attempt to out space him with fair. You will get NOWHERE. Bowser's ftilt is pretty fast for him and will easily knock you out of his area, it also beats out Jiggs' fair, so simply abuse your mobility with bair and pound.
Bowser's side b (Black hole) is a move that Jiggs struggles with a painful amount, simply because of two reasons.
No move Jigglypuff has can outrange it
It has grab armour frames
These two factors play a major role in this match up and will really cut down your approaches for an aerial assault. Your best option is to bait Bowser into doing this move, then punishing with pound, if you misspace your pound, your eating a side b, doing a whopping 18% fresh! Watch out! Bowser can cancel the lag of this move by jumping as he is about to hit the ground, this acts as an infinite jump, but having near to consistant grab armor frames, a kill move active consistantly and a ton of mobility to boot. This move will kill Jiggs around 130 with good DI.
Bowser has a variety of options to deal with Jigglypuff when she attempts to get in, these consistant of well spaced fairs, jab cancels, black holes and most important, UpB OoS. UpB OoS is a VITAL move for Bowser in this matchup, he can utilize it's invincibility frames and frame 6 hitbox startup to knock away Jiggs whenever she tries to approach. Bowser can sit in his shield, bait an attack and simply UpB OoS you. To get around this, well spaced fairs and bairs work like a BLESSING in this MU, you can punish UpB's ending lag and punish him for it.
Now, Bowser's blind spot. Luckily for us, this makes the MU ALOT more bearable and is definatly game changing for us, otherwise this MU would be at least 65-35 his favor. Bowser's blind spot is below him, so this means, he is pure and utter juggle bait. Bowser's down aerial, has been named as one of the worst moves in the entire game. It has literally no use to it at all, it doesn't suck people into it for a good damage racker, it doesnt kill, space, has a ton of ending and start up lag on, lacks hitboxes and most importantly does like 3% if you don't even bother inputting a command, so needless to say, Bowser will never ever ever use this move, and will simply attempt to air dodge into the ground since his down special, Bowser Bomb, is also dripping with start up lag and you should never get his by this move. Whenever Bowser becomes airborne, if he isn't eating at least 30-40% EVERY TIME, you are doing it wrong, and need to rethink your strategy against this guy.
Bowser has a grab release combo on nearly every character, Jigglypuff is one of many who gets a pretty nasty one from Bowser. If a Bowser manages to grab you (which shouldn't be happening, if it is, practise your spacing on larger characters) he can force an air release on you, and then buffer a free uair from it! This can end your stock at around 70-80 on FD and is pretty nasty, so for god sake practise your spacing and don't pound his gigantic shield, he will easily be able to punish you with this.
Now, Bowser is the heaviest character in the entire game, so as you can imagine, killing him is going to be pretty annoying and it won't happen until AT LEAST 140% with bad DI. During the time you can kill Bowser, your bair, uair pound and possibly fair should be to some extent stale, so gimping Bowser is a top priority. Once you manage to get Bowser airborne (a mixed up utilt is a good launcher for you), you can literally carry him off stage. A mix up of nairs, bairs and fairs should be more then enough to get him off stage and is a pretty good strategy to get rid of Bowser pretty early. However, this is far easier said then done, a good Bowser won't let this happen normally, he will keep his shield to the point where it can't be poked, spacing black holes and UpB OoS will really keep him in a safe position.
Once you get a percentage lead against Bowser, try your best to keep it, forcing Bowser to approach is a key ingredient to win this matchup. Air camping is always an option, but be wary of the disjoint on Bowser's uair if he tries to chase you, it has very misleading range. If Bowser has the percentage lead, he can easily just use his side b to to suicide you if you fail to direct this move, and it can be devasting.
Here are the kill moves Bowser has at his disposal:
Black Hole (SideB),Bowser Bomb (DownB),Fortress (UpB),Fair,Bair,Uair,Dtilt,Ftilt,Utilt,Usmash,Dsmash,Fsmash.
All of those moves are capable of KOing, not all of them will be used obviously, but don't think that your safe just because his ftilt, sideb or fair are stale, he can easily pull out a surprise bair and end a stock lower then 100%.
For stages that you wish to pick, I recommend Rainbow Cruise. This stage is going to be a lifeline for you, and you will destroy Bowser here. His lack of natural mobility will be a pain for him to keep up and overall his lack of a good vertical recovery will make it a pain for him to move around on the platforms and to keep up with the stage at the same time, take advantage of this, if you see him reaching for a platform, keep him off of it, don't let him keep his ground anywhere, always keep the pressure on!
Ban Yoshi's Island [Brawl]. This move is a haven for Bowser and it's like it was designed for him. The survival ghost can stop your gimps in their tracks, the platform above the stage is a pain for Jiggs' since Bowser and utilt and uair through it and really put a hurting your percentage. The dips on the edges can allow Bowser to cancel his ledge approaches really early such as SideB.
Overall, this is a pretty annoying for Jigglypuff but is more then doable. You have to be PATIENT, don't rush into him, you will get punished. Getting a percentage lead is a must because it forces Bowser to approach you and cuts down his defensive options. Beware of the range on Bowser's side B, it is very very disjointed and will end your stocks extremely quickly.