I was a Teenage Seal is another episode in Ed, Edd, n Eddy's Ed-ventures Chronicles.
Mako accidentally transforms into a seal after being injected with seal plasma.
Mako is all set to leave for the jellyfishing convention in Ukelele Bottom that weekend. Realizing that he will not be able to take Sidney, Mako leaves Sidney in Brian's responsibility. Mako takes Brian around his house, telling him that he will have to feed Sidney for three days. There are very large cans of seal food with the words "morning", "afternoon" and "night" written on them, so that Brian will be able to keep track. Eager to get rid of both of them, Brian lies and says that he will do it to get Mako to leave. He does, and Brian runs out of Mako's house and sits in a lounge chair for the whole weekend, thus ignoring Sidney. He soaks up plenty of sun, but Sidney is left in the house, looking longingly in the direction where Mako left, horribly neglected. When Mako gets back, Brian suddenly remembers that he was supposed to take care of Sidney. However, when he goes to get Sidney, he finds him very sick, due to lack of food, water, and attention. Brian, thinking he will be able to help, tried to give Sidney some food. However, Sidney is so weak from waiting for Mako to come home, he is limp in Brian's arms and will not eat. Brian puts Mako down as he hears Mako coming back, and tries to force feed Sidney. When he hears Mako coming in, Brian gives up and puts all of Sydney's food into his mouth. He greets Mako awkwardly, and explains that he was only checking on Sidney. Just as Brian is about to leave, a smirk on his face, Sidney slowly enters the room. Mako realizes that something is wrong, and quickly calls Fluttershy. She comes over to Mako's house, and gives Mako a syringe full of seal plasma. Mako asks Brian to give Sidney the plasma, as he is squeamish. Brian reluctantly agrees and, while trying to inject Sidney, accidentally injects Mako with seal plasma causing Mako to worry about the consequences. Upon realizing that Sidney only needed water, Brian leaves telling Mako not to worry. Sometime later, Mako starts acting slow and somewhat like a seal, as well as eating Sidney's food himself. When he goes to the bathroom, he transformed into a seal! Afterwards, he goes over to the Griffin's house to get help, but Brian, Vinny, Eddy, Ed, Rainbow, Human Rainbow, Human Fluttershy, Zoe Trent, Gail Trent, Pepper Clark, & Penny Ling are terrified of the fact that Mako turned into a seal because of his lousy aim and Brian throws the seal plasma away and he tries to reassure himself, but he hears Mako at the door and starts blocking the doors and windows and they tried to run and hide from Mako. He chases them for help, but they keep running from they're lives thinking they're under attack which ultimately makes a mess of the house. Amongst the chaos, Brian accidentally injects himself with the plasma, turning him into a seal as well. The ending has Sidney, Mako, and Brian barking to the tune of "Blow the man down" on top of a fence. Adagio Dazzling, annoyed by this, yells at them to shut up and throws her boot at Brian. Sydney and Mako continue to bark, but Brian tries to barking the rest that ends after fading to black.
- This episode is based off of the SpongeBob episode, "I Was a Teenage Gary".