For the marshmallow, take about 15 medium size marshmallows, and put them in the freezer for 30 minutes. When you take them out, find a nice place and get on all fours. Live up your asshole, then take a marshmallow and dip it in some water (just a little) and put it in your backside. This should go in way easier than the bananas. More @Wikipedia
Hover over any link to get a description of the article. Please note that search keywords are sometimes hidden within the full article and don't appear in the description or title.