Mario,Luigi, 4D counterparts,MM54321 and all his friends and fans
Into the Fourth Dimension
Dowser is the 4th dimension counterpart of Bowser and king of the Roopas. He was introduced as an obvious shadow in ITFD Part 6 in the Roopa Clown Car and then appered as himself at the end of Part 7. From what he said, he will be trouble in Part 8, which he did and Mario fought him at Shark Plant Pond. He had more D-Stars than Mario & friends, but he lost after YouTubers collected more D-Stars and Mario defeated him. Afterwards, Mario beat Dowser's Dimensional Swamp and unlocked 4D Tower, where he kidnapped the plumber so that Dimentio can turn him into Mr. M. Later, Luigi went to Mini Castle Bleck and found Dowser's D-Bully, and Dowser told Luigi that it's his fault Mario became Mr M. After Luigi destroyed the D-Bully, Mr. M spied on the heroes and was interested in MarioMario54321's words. Later Mr. M, Dowser and Bob-omberman attacked MM and let Dimentio turn him into Mr. Mx2. Dimentio later told his minions that he wants to destroy all Dimensions, making Bob-omberman and Dowser quit being his minions. After Mr. M and Mr. Mx2 turned back to normal, the heroes went to Dowser's Lava Falls and, with Dowser's permission, let them take his D-Stars. Dowser and Bob-omberman went to Dimentio's lair when the heroes where there, and with Dimentio telling everyone his true plan was to make new dimensions, Dowser re-sided with the clown, while Bob-omberman didn't because he learned from the Mistress of Music that life was not all about Bombs and destroying. Dimentio merged with Dowser to become Dowmentio. After Dowmentio beat Mario, Dowmentio attempted to use the Mega D-Star to destroy the Fourth Dimension but Mario got back up and destoryed Dowmentio, making Dowser get pushed out into space. However, despite getting blasted off, Dowser appeared in "5 is Real, the Secret of the Fourth Dimension" but was stopped by Mario who got his Replica D-Star. Afterwards, while the Youtube Rangers where having a party in the Fourth Dimension, Dowser came to interfere with it, but was beaten up by Starman3.
Dowser later appears in Back to the Fourth Dimension, possibly as the main antagonist. He may be a secondary one, however, and has been seen planning to steal the Rainbow Shards to get revenge on Quario and his friends and rule the Fourth Dimension with an unknown ally.