The first is the possibility of having three Pikmin carry a single one-weight pellet. In some rare cases, when one Pikmin attacks the leaf of a Pellet Posy, and two are attacking it from the ground, they will all carry the pellet.
The second is having two one weight pellets go into each other. If two Pikmin are carrying both pellets and they run into each other, it looks like four Pikmin are carrying a single weight pellet.
The third is the chance of having the sides of a large pellet point up and the Pikmin carrying it will appear to be standing in mid-air while holding it. They'll bring it back to the Onion normally. Simply call them back and order them to pick it up again to fix it. This also happens with some ship parts such as the Libra. One good example for this glitch would be minute 2:39 of this video:
The fourth glitch happens when a pellet is beneath a bridge suspended over water, but the bridge is still being constructed, and the pellet has to be in front of the rolled-up stick pile that forms the bridge's tip. How far away is irrelevant, as long as it will still be beneath the future bridge. As an example, the one with a Yellow Wollywog near the island with the Massage Machine in The Distant Spring would work well. When the Bridge comes to the point where the pellet is, the Pikmin that are working may stop working and move in circles around the spot where the pellet is under the bridge, and try to grab it. They can be called back and ordered to finish the bridge, but if not, they will sigh, showing that their attempt to grab the object failed, and then become idle. In some rare cases the Pikmin can fall through the bridge, but instead of drowning, will sit safely on top of the pellet. If such a Pikmin is whistled at multiple times, it will fall off the side of the pellet and start drowning.
A fifth glitch also occurs, however this glitch only occurs in the New Play Control! version of Pikmin, as it's unknown if it can happen in the original Gamecube version. This glitch happens anywhere when Pikmin, carrying a large item, walk into a group of Pellet Posies (For example, to the left of the landing site in the Forest of Hope, where the ledge with the Shock Absorber is). When the Pikmin walk into the patch of Pellet Posies, the Pellet Posies may act like a, "cage", and the Pikmin will carry the object while walking in place, and the noise that ship parts make when they are set down will play continuously. Calling the Pikmin back and ordering them to cut down the Pellet Poses, or to manually do it with Olimar, will allow the Pikmin to proceed to the Ship.
Pellets can also cause the Crushing glitch.