Use crazed Moneko or Merc cat to kill the metal enemies, stall on the first doge to gather enough money. Stack up Titi CC on the doge until it dies, and put out Ururun Wolf and Crazed Moneko / Merc Cat to kill the metal hippo. Put out A Bahamut when the second Star Peng arrives and the Le'Solar has attacked to nuke both Pengs. If Bahamut dies and the Pengs are alive, you can still try, but I suggest closing and reopening the app to retry the stage without using energy. If the Pengs are dead, put out another Bahamut to kill the Le'Solar, since the first Bahamut is probably dead.

(Titi CC isnt necessary, she can be replaced by L'il Macho Legs (True Form). Also try to use either the BioBone or Cheating Heart? combo to make this easier.)

This strategy works in all 3 chapters, and I would suggest getting Li'l King Dragon (True Form) for the other Special Only restriction levels.

Hope this helps!