The Gundam franchise launched the "realistic" mecha genre, recontextualizing giant robots from bulbous mechanical friends to military hardware and launched a multi-million dollar model community that has obsessive builders across the world. One such builder by the name of J.G.C. Justin Gundam Custom has made a name for himself with these crossover homages that take standard Gundam models and remakes them as pop-culture homages. If these float your boat he's definitely a guy worth following on facebook.
In case you're curious, here's what a typical model looks like before the customizations:
3. Saitama and Genos from "One Punch Man"
4. Darth Vader
5. The Teenage Mutant Ninja Turtles