Megaton Blast is a celebration stage that features enemies from seasonal and monthly stages. This stage features Chicka Fry from A Cultured Festival event, Blitzen from St. Jolly Nick event, Carny Otta from Summer Diary Event, and Mammothe and his guards Icy Doge and Snowball from Cats in Snow Event.
The stage opens with 2 Chicka Fries, supported by Icy Doges and Snowballs. Some Firework Guys will also appear.
If the cats have their True Forms achieved that'll be an advantage to you. You must save A LOT of money, so use it wisely. Don't stop spamming your meatshields until Chicka Fries dies, cause if you stop, Chicka would lower the attack of your cats. The rest is not a problem until you hit the base. Use the money you saved to take out stronger meatshields and attackers. Close range attackers will probably die because of Carny Otta's attacks.
Lure them near your base and send out a Bahamut, that'll deal with some of the enemies. Don't forget to send out other attackers too cause while Bahamut is charging, he can get knockbacked. Take out more shockwave attackers. If you have reached that far, only some Firework Guys and Mamooth must be near your base. Use long ranged attackers to defeat Mamooth, and the rest is no problem.
Following the video below, you must have Cap'n Ahab and Moby Dick. Send out a cat to defend from the Snowballs, like Crazed Fish Cat. When the Chicka Fries come, spam your meatshields and shockwave attackers.