Think of some strange names for alien creatures... the alien names must be strings of non-words with the same initial sound, for example:
Ping pang poo pop
Mig mog mully mo
Fo fi fandle fee
Write them down as a reminder.
Talk to your child about the names. Make the pattern clearer by emphasising the initial sound of an alien's name. Draw your child's attention to the way you start each word with the shape of your lips, teeth and tongue.
Help your child to imagine what the strange creatures might look like and have a go at making some.
There are some ideas below but you can be as creative as you like!