Super Mario Galaxy 2 #58 - Comet Tôket 7

3 More Power Stars in this video, but they are all about collecting Purple Coins!. Yeah, I usually get 4 Stars, but I decided to miss 2 purple coins on a slide and wasted some much needed time... ugh... Also, note for next time: tell Player 2 to stop mashing the 'A' button!

Tall Trunk's Purple Coin Slide
The thing about some Purple Coin Comets are that you need to grab only 100 of the Purple Coins available. There is 40 extra. So getting every single coin may be impossible but there is some room for error. Of course, if you miss 41 or more coins, then you must try again. Also, there's a 1-UP Mushroom behind the tree. Don't know how Danzo knew that was there...

Purple Coin Spin Speed Run
100 Purple Coins to collect, but spread in the nine different cells. The timed gravity-switching mechanic is still in effect. Though if you want to have an easier time, remember that you can triple jump, side-flip and wall-kick while holding the Spin Drill. Of course, a Co-Star Luma will help you scavenge coins faster.

Bulb Berry's Purple Coin Glow
Back in the same setting, but just 100 Purple Coins to deal with. they aren't terribly hard to grab and there's no time limit, so you can take your time if you need to. The bulb berry lasts around fifteen seconds, plenty of time to eat another in time. Just remember that you do NOT want to jump off of Yoshi while standing on invisible platforms. The Bulb Berry's effects will vanish instantly if you do.