Cook pasta in a large pot of boiling water for 10 minutes. Then drain pasta rinse under cold water. Place pasta in a large Tupperware to cool.
MAKE AND COOL PINEAPPLE CUSTARD:
In a medium saucepan over medium heat whisk together pineapple juice, sugar, flour, egg, egg yolk, and salt.
Bring the mixture to a low boil while whisking every minute. Continue to cook until it has thickened, about another 1-2 minutes. Transfer the mixture to a bowl, stir in the lemon juice, and allow it to cool.
Once the pasta and custard have cooled, add the custard to the pasta and stir to combine. Cover and chill in the refrigerator for at least 2 hours, but overnight is better.
ADD IN FRUIT AND FLUFF:
Beat heavy cream until stiff peaks form. Add marshmallow creme and beat on medium speed until incorporated about 30 seconds.
Transfer pasta mixture to a large serving bowl. Fold in whipped cream mixture, drained fruit, marshmallows, and coconut.
GARNISH AND SERVE:
Garnish with piped whipped cream, mandarin slices, and maraschino cherries (all optional). Serve or chill until ready to serve.